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  • Geophysics  (202)
  • 2000-2004  (202)
  • 2002  (202)
  • 1
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    Initiation of shear instability in three-dimensional elastodynamics (2002)
    In:  J. Geophys. Res., London, Am. Soc. Mech. Eng., vol. 107, no. B7, pp. ESE 4-1 to ESE 4-18, pp. 2147, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 2002
    Keywords: Seismology ; Three dimensional ; Dynamic ; Source ; Modelling ; Fracture ; 7209 ; Earthquake ; dynamics ; and ; mechanics ; 3230 ; Mathematical ; Geophysics: ; Numerical ; solutions ; 7260 ; Seismology: ; Theory ; and ; modeling ; 7299 ; 3299 ; Mathematical ; Geophysics ; JGR
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Simulating the Dynamics of Earth's Core: Using NCCS Supercomputers Speeds Calculations (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: If one wanted to study Earth's core directly, one would have to drill through about 1,800 miles of solid rock to reach liquid core-keeping the tunnel from collapsing under pressures that are more than 1 million atmospheres and then sink an instrument package to the bottom that could operate at 8,000 F with 10,000 tons of force crushing every square inch of its surface. Even then, several of these tunnels would probably be needed to obtain enough data. Faced with difficult or impossible tasks such as these, scientists use other available sources of information - such as seismology, mineralogy, geomagnetism, geodesy, and, above all, physical principles - to derive a model of the core and, study it by running computer simulations. One NASA researcher is doing just that on NCCS computers. Physicist and applied mathematician Weijia Kuang, of the Space Geodesy Branch, and his collaborators at Goddard have what he calls the,"second - ever" working, usable, self-consistent, fully dynamic, three-dimensional geodynamic model (see "The Geodynamic Theory"). Kuang runs his model simulations on the supercomputers at the NCCS. He and Jeremy Bloxham, of Harvard University, developed the original version, written in Fortran 77, in 1996.
    Keywords: Geophysics
    Type: 1999 NCCS Highlights; 84-89
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  • 3
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    The Earth Gravitational Model 1996: The NCCS: Resource for Development, Resource for the Future (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: For centuries, men have attempted to understand the climate system through observations obtained from Earth's surface. These observations yielded preliminary understanding of the ocean currents, tides, and prevailing winds using visual observation and simple mechanical tools as their instruments. Today's sensitive, downward-looking radar systems, called altimeters, onboard satellites can measure globally the precise height of the ocean surface. This surface is largely that of the equipotential gravity surface, called the geoid - the level surface to which the oceans would conform if there were no forces acting on them apart from gravity, as well as having a significant 1-2- meter-level signal arising from the motion of the ocean's currents.
    Keywords: Geophysics
    Type: 1999 NCCS Highlights; 78-83
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  • 4
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    Media Calibration in the Deep Space Network: A Status Report (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: A new media calibration system (MCS) has been implemented at the Goldstone complex of the DSN (Deep Space Network). It is intended to calibrate the delay of radio signals imposed by the neutral atmosphere. The system provides periodic measurements of both the static dry and fluctuating wet components of this delay. In particular, the system will calibrate the fluctuations in line of sight path delay due to atmospheric water vapor that we believe will dominate the error budget for several radio science and radio astronomy experiments. We have compared two of these media calibration systems with a connected element interferometer on a 21 km baseline. In this report we describe a total of 30 observations in which a radio source was tracked for an hour or more and the delay residuals then calibrated using the MCS. The accuracy of the comparison appears to be limited by systematic errors in the interferometer, which are under investigation. However, our results do indicate that the MCS can meet or exceed the two-way Allan standard deviation specification of 1.5 x 10( exp -15) on time scales of 2,000 - 10,000 sec, as required by the Cassini GWE (Gravitational Wave Experiment) for two way Doppler tracking.
    Keywords: Geophysics
    Type: International VLBI Service for Geodesy and Astrometry General Meeting Proceeding; 194-198; NASA/CP-2002-210002
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  • 5
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    Geodetic Results from Mark 4 VLBI (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: We present geodetic results of a series of 30 VLBI experiments recorded in Mark 4 mode at rates of 128 and 256 Mbps. The formal uncertainties of UT1, polar motion, and nutation offsets derived from these experiments are better than the corresponding uncertainties from NEOS-A experiments by a factor of 1.3-2. Baseline length repeatability for the series of 32 experiments over a period of one year is about 0.9 ppb. For comparison, NEOS-A length repeatability is about 1.4 ppb. We will discuss optimal use of Mark 4 in the design of future observing networks.
    Keywords: Geophysics
    Type: International VLBI Service for Geodesy and Astrometry General Meeting Proceeding; 50-54; NASA/CP-2002-210002
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  • 6
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    The New IERS Special Bureau for Loading (SBL) (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: Currently, the establishment of the International Earth Rotation Service (IERS) Special Bureau for Loading (SBL) is in progress as part of the IERS Global Geophysical Fluids Center (GGFC). The main purpose of the SBL is to provide reliable, consistent model predictions of loading signals that have been thoroughly tested and validated. The products will describe at least the surface deformation, gravity signal and geo-center variations due to the various surface loading processes in reference frames relevant for direct comparison with existing geodetic observing techniques. To achieve these goals, major scientific advances are required with respect to the Earth model, the theory and algorithms used to model deformations of the Earth as well as improvements in the observational data related to surface loading.
    Keywords: Geophysics
    Type: International VLBI Service for Geodesy and Astrometry General Meeting Proceeding; 287-291; NASA/CP-2002-210002
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  • 7
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    Effect of Gravity on the Near Field Flow Structure of Helium Jet in Air (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: Experiments have shown that a low-density jet injected into a high-density surrounding medium undergoes periodic oscillations in the near field. Although the flow oscillations in these jets at Richardson numbers about unity are attributed to the buoyancy, the direct physical evidence has not been acquired in the experiments. If the instability were indeed caused by buoyancy, the near-field flow structure would undergo drastic changes upon removal of gravity in the microgravity environment. The present study was conducted to investigate this effect by simulating microgravity environment in the 2.2-second drop tower at the NASA Glenn Research Center. The non-intrusive, rainbow schlieren deflectometry technique was used for quantitative measurements of helium concentrations in buoyant and non-buoyant jets. Results in a steady jet show that the radial growth of the jet shear layer in Earth gravity is hindered by the buoyant acceleration. The jet in microgravity was 30 to 70 percent wider than that in Earth gravity. The microgravity jet showed typical growth of a constant density jet shear layer. In case of a self-excited helium jet in Earth gravity, the flow oscillations continued as the jet flow adjusted to microgravity conditions in the drop tower. The flow oscillations were however not present at the end of the drop when steady microgravity conditions were reached.
    Keywords: Geophysics
    Type: Sixth Microgravity Fluid Physics and Transport Phenomena Conference: Exposition Topical Areas 1-6; Volume 2; 475-486; NASA/CP-2002-211212/VOL2
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  • 8
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    Consequences of Coupled Electromagnetic-Gravitational Fields (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: In the late 1980s there was a flurry of activities involving the newly discovered high Tc superconductors in the development of new devices such as more efficient current transmission, transformers, generators, and motors. One such developmental project by Podkletnov in 1992 noted some small, anomalous gravitational behaviors. A following unpublished paper by Podkletnov 1995 provided data with larger effects using a larger (approx. 25 cm) superconducting disk. Unfortunately this disk was extremely fragile and was broken beyond repair. To date, these experiments have not been successfully repeated because of the difficulties of producing stable, durable (and fired) superconducting disks. This problem with firing these disks has been solved by Li. What remains is to install the disk in "motor", at superconducting temperatures in the presence of appropriately tailored magnetic fields.
    Keywords: Geophysics
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XLVIII-1 - XLVIII-6; NASA/CR-2002-211840
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  • 9
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    Wide-Band Data Transmission System Expected in the Next Generation Space VLBI Mission: VSOP-2 (2002)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: Following the success of the VLBI Space Observatory Program (VSOP), a next generation space VLBI mission (VSOP-2) is currently being planned. We expect the data rate of more than 1 Gbps to get more sensitivity. Here we will present: (1) How to sample the data (on board), including the radiation test results which show we can have the 10 Gbps sampler LSI which can use in space; (2) Possibility of the bit rate more than 1 Gbps to downlink the VLBI data. We studied the link budget for the wide band data transmission, and discussed the various ideas which can get more than 1 Gbps; and (3) What kind of VLBI tracking station and recording system will be expected for the VSOP-2 mission? We will present the idea of using normal radio telescopes as a tracking station, and also review the possibility of recording and processing at the tracking stations and correlators.
    Keywords: Geophysics
    Type: International VLBI Service for Geodesy and Astrometry General Meeting Proceeding; 175-178; NASA/CP-2002-210002
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  • 10
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    Upper Tropospheric Ozone Between Latitudes 60S and 60N Derived from Nimbus 7 TOMS/THIR Cloud Slicing (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: This study evaluates the spatial distributions and seasonal cycles in upper tropospheric ozone (pressure range 200-500 hPa) from low to high latitudes (60S to 60N) derived from the satellite retrieval method called "Cloud Slicing." Cloud Slicing is a unique technique for determining ozone profile information in the troposphere by combining co-located measurements of cloud-top, pressure and above-cloud column ozone. For upper tropospheric ozone, co-located measurements of Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) above-cloud column ozone, and Nimbus 7 Temperature Humidity Infrared Radiometer (THIR) cloud-top pressure during 1979-1984 were incorporated. In the tropics, upper tropospheric ozone shows year-round enhancement in the Atlantic region and evidence of a possible semiannual variability. Upper tropospheric ozone outside the tropics shows greatest abundance in winter and spring seasons in both hemispheres with largest seasonal and largest amounts in the NH. These characteristics are similar to lower stratospheric ozone. Comparisons of upper tropospheric column ozone with both stratospheric ozone and a proxy of lower stratospheric air mass (i.e., tropopause pressure) from National Centers for Environmental Prediction (NCEP) suggest that stratosphere-troposphere exchange (STE) may be a significant source for the seasonal variability of upper tropospheric ozone almost everywhere between 60S and 60N except in low latitudes around 10S to 25N where other sources (e.g., tropospheric transport, biomass burning, aerosol effects, lightning, etc.) may have a greater role.
    Keywords: Geophysics
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  • 11
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    Tidal Models In A New Era of Satellite Gravimetry (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The high precision gravity measurements to be made by recently launched (and recently approved) satellites place new demands on models of Earth, atmospheric, and oceanic tides. The latter is the most problematic. The ocean tides induce variations in the Earth's geoid by amounts that far exceed the new satellite sensitivities, and tidal models must be used to correct for this. Two methods are used here to determine the standard errors in current ocean tide models. At long wavelengths these errors exceed the sensitivity of the GRACE mission. Tidal errors will not prevent the new satellite missions from improving our knowledge of the geopotential by orders of magnitude, but the errors may well contaminate GRACE estimates of temporal variations in gravity. Solar tides are especially problematic because of their long alias periods. The satellite data may be used to improve tidal models once a sufficiently long time series is obtained. Improvements in the long-wavelength components of lunar tides are especially promising.
    Keywords: Geophysics
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  • 12
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    Stratospheric Analysis and Forecasting in the Northern Winter of 1999/2000: The NASA DAO's GEOS-3 System (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: An evaluation is presented of the performance in the northern winter 1999/2000 of the GEOS-3 troposphere-stratosphere data assimilation system (DAS). The impacts of the two main input data types are assessed: upper-air soundings (sondes) provide wind and temperature information and satellite-based (Tiros Operational Vertical Sounders: TOVS) give estimates of the thermal structure. It is shown that in the low stratosphere (300-70hPa) the analyses are generally slightly warmer than the sonde data, but colder than the TOVS data; this relationship reverses between 70 and 10 hPa. There are geographical biases, related to the spatial and temporal coverage of the observation types and to the statistical weights assigned to them in the DAS. Forecasts show a tendency to reduce zonal asymmetries in the atmospheric flow and to suppress stratospheric temperature minima. In the DAS, the analysis increments compensate for this, but it leads to important biases in the multi-day forecasts. The analysis increments are as large as the diabatic forcing in the lower polar stratosphere, indicating a substantial model bias. The results provide important insights into the roles of different data types and the circulation model in producing accurate analyses for studies of polar chemistry and physical processes.
    Keywords: Geophysics
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  • 13
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    The 1998-2000 SHADOZ (Southern Hemisphere ADditional OZonesondes) Tropical Ozone Climatology (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: This is the second 'reference' or 'archival' paper for the SHADOZ (Southern Hemisphere Additional Ozonesondes) network and is a follow-on to the recently accepted paper with similar first part of title. The latter paper compared SHADOZ total ozone with satellite and ground-based instruments and showed that the equatorial wave-one in total ozone is in the troposphere. The current paper presents details of the wave-one structure and the first overview of tropospheric ozone variability over the southern Atlantic, Pacific and Indian Ocean basins. The principal new result is that signals of climate effects, convection and offsets between biomass burning seasonality and tropospheric ozone maxima suggest that dynamical factors are perhaps more important than pollution in determining the tropical distribution of tropospheric ozone. The SHADOZ data at (〈http://code9l6.gsfc.nasa.gov/Data_services/shadoz〉) are setting records in website visits and are the first time that the zonal view of tropical ozone structure has been recorded - thanks to the distribution of the 10 sites that make up this validation network.
    Keywords: Geophysics
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  • 14
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    An X-ray Investigation of the NGC 346 Field in the SMC (2): The Field Population (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We present results from a Chandra observation of the NGC 346 cluster, the ionizing source of N66, the most luminous H II region and the largest star formation region in the SMC. In the first part of this investigation, we have analysed the X-ray properties of the cluster itself and the remarkable star HD 5980. But the field contains additional objects of interest. In total, 79 X-ray point sources were detected in the Chandra observation and we investigate here their characteristics in details. The sources possess rather high HRs, and their cumulative luminosity function is steeper than the SMC's trend. Their absorption columns suggest that most of the sources belong to NGC 346. Using new UBVRI imaging with the ESO 2.2m telescope, we also discovered possible counterparts for 36 of these X-ray sources. Finally, some objects show X-ray and/or optical variability, and thus need further monitoring.
    Keywords: Geophysics
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  • 15
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    Airborne Lidar Measurements of Aerosol Optical Properties During SAFARI-2000 (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The Cloud Physics Lidar (CPL) operated onboard the NASA ER-2 high altitude aircraft during the SAFARI-2000 field campaign. The CPL provided high spatial resolution measurements of aerosol optical properties at both 1064 nm and 532 nm. We present here results of planetary boundary layer (PBL) aerosol optical depth analysis and profiles of aerosol extinction. Variation of optical depth and extinction are examined as a function of regional location. The wide-scale aerosol mapping obtained by the CPL is a unique data set that will aid in future studies of aerosol transport. Comparisons between the airborne CPL and ground-based MicroPulse Lidar Network (MPL-Net) sites are shown to have good agreement.
    Keywords: Geophysics
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  • 16
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    Charge Generation and Propagation in Igneous Rocks (2002)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Various electrical phenomena have been reported prior to or concurrent with earthquakes such as resistivity changes, ground potentials, electromagnetic (EM), and luminous signals. Doubts have been raised as to whether some of these phenomena are real and indeed precursory. One of the reasons for uncertainty is that, despite decades of intense work, there is still no physically coherent model. Using low- to medium-velocity impacts to measure electrical signals with microsecond time resolution, it has now been observed that when dry gabbro and diorite cores are impacted at relatively low velocities, approximately 100 m/s, highly mobile charge carriers are generated in a small volume near the impact point. They spread through the rocks, causing electric potentials exceeding +400 mV, EM, and light emission. As the charge cloud spreads, the rock becomes momentarily conductive. When a dry granite block is impacted at higher velocity, approximately 1.5 km/s, the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. After the sound waves have passed, the surface of the granite block becomes positively charged, suggesting the same charge carriers as observed during the low-velocity impact experiments, expanding from within the bulk. During the next 2-3 ms the surface potential oscillates, indicating pulses of electrons injected from ground and contact electrodes. The observations are consistent with positive holes, e.g., defect electrons in the O(2-) sublattice, traveling via the O 2p-dominated valence band of the silicate minerals. Before activation, the positive holes lay dormant in the form of electrically inactive positive hole pairs (PHP), chemically equivalent to peroxy links, O3X/OO\XO3, with X=Si(4+), Al(3+), etc. PHPs are introduced into the minerals by way of hydroxyl,O3X-OH, which all nominally anhydrous minerals incorporate when crystallizing in H2O-laden environments. The fact that positive holes can be activated by low-energy impacts, and their attendant sound waves, suggests that they can also be activated by microfracturing. Depending on where in the stressed rock volume the charge carriers are activated, they will form rapidly moving or fluctuating charge clouds that may account for earthquake-related electrical signals and EM emission. Wherever such charge clouds intersect the surface, high fields are expected, causing electric discharges and earthquake lights.
    Keywords: Geophysics
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  • 17
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    Pulsar Polar Cap Heating and Surface Thermal X-ray Emission (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We investigate the production of electron-positron pairs by inverse Compton scattered (ICS) photons above a pulsar polar cap (PC) and calculate surface heating by returning positrons. This paper is a continuation of our self-consistent treatment of acceleration, pair dynamics, and electric field screening above pulsar PCs. We calculate the altitude of the inverse Compton pair-formation fronts, the flux of returning positrons, and present the heating efficiencies and X-ray luminosities. We revise pulsar death lines implying cessation of pair formation, and present them in surface magnetic field-period space. We find that virtually all known radio pulsars are capable of producing pairs by resonant and nonresonant ICS photons radiated by particles accelerated above the PC in a pure star-centered dipole field, so that our ICS pair death line coincides with empirical radio pulsar death. Our calculations show that ICS pairs are able to screen the accelerating electric field only for high PC surface temperatures and magnetic fields. We argue that such screening at ICS pair fronts occurs locally, slowing but not turning off acceleration of particles until screening can occur at a curvature radiation (CR) pair front at higher altitude. In the case where no screening occurs above the PC surface, we anticipate that the pulsar gamma-ray luminosity will be a substantial fraction of its spin-down luminosity. The X-ray luminosity resulting from PC heating by ICS pair fronts is significantly lower than the PC heating luminosity from CR pair fronts, which dominates for most pulsars. PC heating from ICS pair fronts is highest in millisecond pulsars, which cannot produce CR pairs, and may account for observed thermal X-ray components in the spectra of these old pulsars.
    Keywords: Geophysics
    Type: The Astrophysical Journal; Volume 568; 862-877
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  • 18
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    Ozone Depletion from Nearby Supernovae (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Estimates made in the 1970's indicated that a supernova occurring within tens of parsecs of Earth could have significant effects on the ozone layer. Since that time improved tools for detailed modeling of atmospheric chemistry have been developed to calculate ozone depletion, and advances have been made also in theoretical modeling of supernovae and of the resultant gamma ray spectra. In addition, one now has better knowledge of the occurrence rate of supernovae in the galaxy, and of the spatial distribution of progenitors to core-collapse supernovae. We report here the results of two-dimensional atmospheric model calculations that take as input the spectral energy distribution of a supernova, adopting various distances from Earth and various latitude impact angles. In separate simulations we calculate the ozone depletion due to both gamma rays and cosmic rays. We find that for the combined ozone depletion from these effects roughly to double the 'biologically active' UV flux received at the surface of the Earth, the supernova must occur at approximately or less than 8 parsecs.
    Keywords: Geophysics
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  • 19
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    Evaluation of Transport in the Lower Tropical Stratosphere in a Global Chemistry and Transport Model (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Off-line models of the evolution of stratospheric constituents use meteorological information from a general circulation model (GCM) or from a data assimilation system (DAS). Here we focus on transport in the tropics and between the tropics and middle latitudes. Constituent fields from two simulations are compared with each other and with observations. One simulation uses winds from a GCM and the second uses winds from a DAS that has the same GCM at its core. Comparisons of results from the two simulations with observations from satellite, aircraft, and sondes are used to judge the realism of the tropical transport. Faithful comparisons between simulated fields and observations for O3, CH4, and the age-of-air are found for the simulation using the GCM fields. The same comparisons for the simulation using DAS fields show rapid upward tropical transport and excessive mixing between the tropics and middle latitudes. The unrealistic transport found in the DAS fields may be due to the failure of the GCM used in the assimilation system to represent the quasi-biennial oscillation. The assimilation system accounts for differences between the observations and the GCM by requiring implicit forcing to produce consistency between the GCM and observations. These comparisons suggest that the physical consistency of the GCM fields is more important to transport characteristics in the lower tropical stratosphere than the elimination bias with respect to meteorological observations that is accomplished by the DAS. The comparisons presented here show that GCM fields are more appropriate for long-term calculations to assess the impact of changes in stratospheric composition because the balance between photochemical and transport terms is likely to be represented correctly.
    Keywords: Geophysics
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  • 20
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    Wavelet Approximation in Data Assimilation (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Estimation of the state of the atmosphere with the Kalman filter remains a distant goal because of high computational cost of evolving the error covariance for both linear and nonlinear systems. Wavelet approximation is presented here as a possible solution that efficiently compresses both global and local covariance information. We demonstrate the compression characteristics on the the error correlation field from a global two-dimensional chemical constituent assimilation, and implement an adaptive wavelet approximation scheme on the assimilation of the one-dimensional Burger's equation. In the former problem, we show that 99%, of the error correlation can be represented by just 3% of the wavelet coefficients, with good representation of localized features. In the Burger's equation assimilation, the discrete linearized equations (tangent linear model) and analysis covariance are projected onto a wavelet basis and truncated to just 6%, of the coefficients. A nearly optimal forecast is achieved and we show that errors due to truncation of the dynamics are no greater than the errors due to covariance truncation.
    Keywords: Geophysics
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  • 21
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    A Comparison of the Age-Spectra from Data Assimilation Models (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably well-isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the diabatic trajectory calculations, the age spectrum is too broad as a result of too much exchange between the tropics and mid-latitudes. The age spectrum determined using the kinematic trajectory calculation is less broad and lacks an age offset; both of these features are due to excessive vertical dispersion of parcels. The tropical and mid-latitude mean age difference between the diabatically and kinematically determined age-spectra is about one year, the former being older. The CTM calculation of the age spectrum using the DAS winds shows the same dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the mean ages determined in a number of previous DAS driven CTM's are too young compared with observations. Finally, we note trajectory-generated age spectra show significant age anomalies correlated with the seasonal cycles, and these anomalies can be linked to year-to-year variations in the tropical heating rate. These anomalies are suppressed in the CTM spectra suggesting that the CTM transport is too diffusive.
    Keywords: Geophysics
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  • 22
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    Amino acids as a source of organic nitrogen in Antarctic endolithic microbial communities (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: In the Antarctic Dry Valleys, cryptoendolithic microbial communities occur within porous sandstone rocks. Current understanding of the mechanisms of physiological adaptation of these communities to the harsh Antarctic environment is limited, because traditional methods of studying microbial physiology are very difficult to apply to organisms with extremely low levels of metabolic activity. In order to fully understand carbon and nitrogen cycling and nutrient uptake in cryptoendolithic communities, and the metabolic costs that the organisms incur in order to survive, it is necessary to employ molecular geochemical techniques such as amino acid analysis in addition to physiological methods.
    Keywords: Geophysics
    Type: American Geophysical Union fall meeting; San Francisco, CA; United States
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  • 23
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    NASA's Interstellar Probe Mission (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: 2002 Spring American Geophysical Union; Washington, DC; United States
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    Error minimization using redundant gravity measurements (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: This paper addresses the problem of redundant gravity measurements for reduction of measurement errors. The approach exploits constraints imposed upon the components of the gravity gradient tensor by the conditions of integrability needed for reconstruction of the gravity potential. It has been demonstrated that the total error of noisy measurements can be reduced by 25% using the best fit into the integrability constraints.
    Keywords: Geophysics
    Type: Geophysics
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    Variations and climatology of CI0 in the polar lower stratosphere from UARS Microwave Limb Sounder measurements (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The Microwave Limb Sounder (MLS) on board the Upper Atmosphere Research Satellite (UARS) measured the global distribution of stratospheric ClO over annual cycles for much of the 1990s, albeit with reduced sampling frequency in the latter half of the decade. Here we present an overview of the interannual and interhemispheric variations in the distribution of ClO derived from UARS MLS measurements, with a particular emphasis on enhancements in the winter polar lower stratosphere.
    Keywords: Geophysics
    Type: Journal of Geophysical Research
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    Following the polar cap magnetic field and heliospheric current sheet as Ulysses descends in latitude (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union, Fall 2002 meeting; San Francisco, CA; United States
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    A global inverse approach to ice mass variations and Earth rheology (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: Weikko A. Heiskanen Symposium in Geodesy; Columbus, OH; United States
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  • 28
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    Gravitational-viscoelastic adjustment to ice sheet change and brittle crustal failure: a link to the MsubW 8.1 March 25, 1998 Antarctic plate earthquake (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Spring Meeting; Washington, DC; United States
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  • 29
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    Ground-based millimeter-wave spectrometer versus UARS microwave limb sounder version 5 retrievals of stratospheric HNO3 over Antarctica (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present the first intercomparison between the two longest records of gas-phase HNO3 vertical profiles in the Antarctic stratosphere.
    Keywords: Geophysics
    Type: Journal of Geophysical Research - atmospheres
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  • 30
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    CO2 exchange coefficients from remotely-sensed wind speed measurements: SSM/I versus QuikSCAT in 2000 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We compare here the air-sea exchange coefficient for C02 estimated with monthly mean wind speed measured by the Special Sensing Microwave Imager (SSM/I), Ks , and by the scatterometer QuikSCAT, Kq, for the year 2000.
    Keywords: Geophysics
    Type: Geophysical Research Letters
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    The influence of recent and ancient Antarctic ice mass change on crustal seismicity (2002)
    In:  Other Sources
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    Publication Date: 2018-06-11
    Keywords: Geophysics
    Type: European Geophysical Society XXVII General Assembly; Nice; France
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  • 32
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    Solar event signatures impressed upon spacecraft radio signals (2002)
    In:  Other Sources
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    Publication Date: 2018-06-11
    Keywords: Geophysics
    Type: American Geophysical Union Spring 2002 Meeting; Washington, DC; United States
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  • 33
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    Ice deformation, growth, and thickness from small-scale ice motion (2002)
    In:  Other Sources
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    Publication Date: 2018-06-11
    Keywords: Geophysics
    Type: European Geophysical Society; Nice; France
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  • 34
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    Dynamical and chemical contributions to variability in microwave limb sounder Arctic stratoshperic column ozone (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Analyses of column ozone above 100 hPa (Col100) derived from Upper Atmosphere Research Satellite Microwave Limb Sounder (MLS) data in February/March 1992-1998 show that about half of the interannual variability in Col100 in the Arctic polar vortex in late winter results from interannual variability in chemical loss. A majority of the remainder results from interannual variability in day-to-day dynamical motions including adiabatic warming/cooling and poleward advection of underlying upper tropospheric subtropical air on short timescales, rather than from variations in descent rates and large-scale transport over the winters. The morphology of Col100 from MLS remains very similar to that in the dynamical models even in the years with most chemical ozone loss. The amount and character of day-to-day variability in dynamical models closely follows that in MLS Col100. Although the morphology of and day-to-day variability in Arctic column ozone are controlled by dynamical processes, chemical ozone loss was a major factor in producing both the low values of and the large interannual variability in Arctic column ozone observed during the 1990s.
    Keywords: Geophysics
    Type: Journal of Geophysical Research - Atmospheres
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  • 35
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    Variability of ozone loss during Arctic winter (1991 to 2000) estimated from UARS Microwave Limb Sounder measurement (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: A comprehensive analysis of version 5 Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) ozone data using a Lagrangian Transport (LT) model provides estimates of chemical ozone depletion for the 1991-1992 through 1997-1998 Arctic winters. These new estimates give a consistent, three-dimensional picture of ozone loss during seven Arctic winters; previous Arctic ozone loss estimates from MLS were based on various earlier data versions and were done only for late winter and only for a subset of the years observed by MLS. We find large interannual variability in the amount, timing, and patterns of ozone depletion and in the degree to which chemical loss is masked by dynamical processes.
    Keywords: Geophysics
    Type: Journal of Geophysical Research - Atmosphere
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    Seasonal ice area and volume production of the Artic ocean: November 1996 through April 1997 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Polar cap boundary layer waves are ELF/VLF electric and magnetic waves detected on field lines just adjacent to the polar cap.
    Keywords: Geophysics
    Type: Journal of Geophysical Research-oceans; Volume 107; no. C10
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    Availability and status of MISR geophysical data products (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: ARM Program Science Team Meeting; St. Petersburg, FL; United States
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  • 38
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    The use of GPS for earth science (2002)
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    Publication Date: 2018-06-08
    Description: With the completion of the Global Positioning System and the appearance of affordable ground and spaceborne receivers, GPS is moving rapidly into the world of Earth science.
    Keywords: Geophysics
    Type: 3rd United Nations/USA Workshop on the Use of Global Navigation Satellite Systems; Santiago; Chile
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  • 39
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    Shock-aurora: FAST and DMSP observations (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union; Washington, DC; United States
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  • 40
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    Bipolar pulse (electron hole) onsets, ion conics, and kinetic Alfven waves in the magnetopause boundary layer: polar (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: European Geophysical Society; Nice; France
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  • 41
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    The Sun's open magnetic flux and its solar cycle variation (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: European Geophysical Society Meeting; Nice; France
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  • 42
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    Near-real-time Jason-1images (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting 2002; San Francisco, CA; United States
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    GRACE level-1 data processing (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; San Francisco, CA; United States
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  • 44
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    Substorm expansion phases during magnetic storms in April 17-23, 2002: IMAGE FUV observations (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: Fall 2002 American Geophysical Union; San Francisco, CA; United States
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  • 45
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    An investigation of recent observed changes in the Earth's oblateness (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: 2002 Fall Meeting of the American Geophysical Union; San Francisco, CA; United States
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  • 46
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    The IERS Special Bureau for the Oceans (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: 2002 Fall Meeting of the American Geophysical Union; San Francisco, CA; United States
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  • 47
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    Laser ranging contributions to monitoring and interpreting Earth orientation changes (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: 13th International Workshop on Laser Ranging; Washington, DC; United States
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  • 48
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    GPS derived seasonal variations at altimeter calibration sites (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Conference; Nice; France
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  • 49
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    CHAMP, mass displacements, and the Earth's rotation (2002)
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    Publication Date: 2018-06-08
    Description: The angular momentum of the atmosphere and oceans change as both the distribution of mass within the atmosphere and oceans changes and as the direction and speed of the winds and currents change.
    Keywords: Geophysics
    Type: CHAMP Mission Results I; Potsdam; Germany|Proceedings of the First CHAMP Science Meeting
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  • 50
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    Dust impacts at Comet P/Borrelly (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: European Geophysical Society; Nice; France
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    The conical fit approach to modeling ionospheric total electron content (2002)
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    Publication Date: 2018-06-08
    Description: The Global Positioning System (GPS) can be used to measure the integrated electron density along raypaths between satellites and receivers. Such measurements may, in turn, be used to construct regional and global maps of the ionospheric total electron content (TEC). Maps are generated by fitting measurements to an assumed ionospheric model.
    Keywords: Geophysics
    Type: Fall Meeting, American Geophysical Society; San Francisco, CA; United States
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  • 52
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    Large-scale ionospheric disturbances during the April 2002 storms (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union 2002 Fall Meeting; San Francisco, CA; United States
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  • 53
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    Uptake of ethyl alcohol vapor in sulfuric acid solutions (2002)
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; San Francisco, CA; United States
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  • 54
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    Applying Geodesy to Geoscience 1 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: Seminar at Earthquake Research Institute; Tokyo; Japan
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  • 55
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    Network issues (2002)
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    Publication Date: 2018-06-08
    Description: In this paper we review the IGS network as it currently exists and its effectiveness in supporting the IGS suite of precise products.
    Keywords: Geophysics
    Type: International GPS Service (IGS) 2002 Workshop Towards Real Time; Ottawa, Ontario; Canada
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  • 56
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    Particle Events as a Possible Source of Large Ozone Loss during Magnetic Polarity Transitions (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The energy deposition in the mesosphere and stratosphere during large extraterrestrial charged particle precipitation events has been known for some time to contribute to ozone losses due to the formation of potential ozone destroying species like NO(sub x), and HO(sub x). These impacts have been measured and can be reproduced with chemistry models fairly well. In the recent past, however, even the impact of the largest solar proton events on the total amount of ozone has been small compared to the dynamical variability of ozone, and to the anthropogenic induced impacts like the Antarctic 'ozone hole'. This is due to the shielding effect of the magnetic field. However, there is evidence that the earth's magnetic field may approach a reversal. This could lead to a decrease of magnetic field strength to less than 25% of its usual value over a period of several centuries . We show that with realistic estimates of very large solar proton events, scenarios similar to the Antarctic ozone hole of the 1990s may occur during a magnetic polarity transition.
    Keywords: Geophysics
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    Evaluation of the MODIS Retrievals of Dust Aerosol over the Ocean during PRIDE (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The Puerto Rico Dust Experiment (PRIDE) took place in Roosevelt Roads, Puerto Rico from June 26 to July 24,2000 to study the radiative and physical properties of African dust aerosol transported into the region. PRIDE had the unique distinction of being the first major field experiment to allow direct comparison of aerosol retrievals from the MODerate Imaging Spectro-radiometer (MODIS) with sunphotometer and in-situ aerosol measurements. Over the ocean, the MODIS algorithm retrieves aerosol optical depth (AOD) as well as information about the aerosols size distribution. During PRIDE, MODIS derived AODs in the red wavelengths (0.66 micrometers) compare closely with AODs measured from sunphotometers, but, are too large at blue and green wavelengths (0.47 and 0.55 micrometers) and too small in the infrared (0.87 micrometers). This discrepancy of spectral slope results in particle size distributions retrieved by MODIS that are small compared to in-situ measurements, and smaller still when compared to sunphotometer sky radiance inversions. The differences in size distributions are, at least in part, associated with MODIS simplification of dust as spherical particles. Analysis of this PRIDE data set is a first step towards derivation of realistic non-spherical models for future MODIS retrievals.
    Keywords: Geophysics
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    Quantifying the information content in GPS slant path delays (2002)
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    Publication Date: 2018-06-08
    Description: We quantify the amount of information on atmospheric water vapor that can be extracted from GPS line of sight measurement, by comparing these measurements to those made with acollocated pointed water vapor radiometer.
    Keywords: Geophysics
    Type: European Geophysical Society General Assembly; Nice; France
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    The influence of recent and ancient Antarctic ice mass change on crustal seismicity (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: European Geophysical Society EGS XXVII General Assembly; Nice; France
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    Reliable Jovian composition, structure, and dynamics measurements from multiple deep entry probes (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: Annual Meeting of the European Geophysical Society; Nice; France
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    Biological iron isotopic fractionations in antarctic endolithis microbial communities (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; San Francisco, CA; United States
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    Estimates of aerosol direct effects on the radiation budget from MISR retrievals (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; San Francisco, CA; United States
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    A database of atmospheric refractivities from GPS radio occultations (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: 13th International Laser Ranging Workshop; Washington, DC; United States
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    Laser ranging contributions to monitoring and interpreting Earth orientation changes (2002)
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    Publication Date: 2018-06-08
    Description: The groundwork for a new field in the geophysical sciences - space geodesy - was laid in the 1960s with the development of satellite and lunar laser ranging systems, along with the development of very long baseline interferometry systems, for the purpose of studying crustal plate motion and deformation, the Earth's gravitational field, and Earth orientation changes. The availability of accurate, routine determinations of the Earth orientation parameters (EOPs) afforded by the launch of the LAser GEOdynamics Satellite (LAGEOS) on May 4, 1976, and the subsequent numerous studies of the LAGEOS observations, has led to a greater understanding of the causes of the observed changes in the Earth's orientation.
    Keywords: Geophysics
    Type: 13th International Workshop on Laser Ranging; Washington, DC; United States
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    Gravitational-viscoelastic adjustment to ice sheet change and brittle crustle failure: a link to the M(sub w) 8.1 March 25 1998 Antarctic plate earthquake (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union Spring Meeting; Washington, DC; United States
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    The interrelationship between magnetic holes (MHs), magnetic decreases (MDs), directional discontinuities (DDs) and Alfven waves as a function of the solar cycle and heliographic latitude: Ulysses (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: European Geophysical Society; Nice; France
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    Offshore Ekman transport and Ekman plumbing off Peru during the 1997-98 El Nino (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: American Geophysical Union; San Francisco, CA; United States
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    Applying Geodesy to Geoscience 1 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Geophysics
    Type: Seminar at Earthquake Research Institute; Tokyo; Japan
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    Factors Affecting the Latitudinal Location of the Intertropical Convergence Zone in a GCM (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The dominant role of the latitudinal peak of the sea surface temperature (SST) in determining the latitudinal location of the intertropical convergence zone (ITCZ) is well-known. However, the roles of the other factors are less well-known and are the topic of this study. These other factors include the inertial stability, the interaction between convection and surface fluxes and the interaction between convection and radiation. Since these interactions involve convection, in a model they involve the cumulus parameterization scheme. These factors are studied with a general circulation model with uniform SST and solar angle. Under the aforementioned model settings, the latitudinal location of the ITCZ is the latitude where the balance of two types of attraction on the ITCZ, both due to earth's rotation, exists. Directly related to the Coriolis parameter, the first type pulls the ITCZ toward the equator and is not sensitive to model design changes. Related to the convective circulation, the second type pulls the ITCZ poleward and is sensitive to model design changes. Due to the shape and the magnitude of the attractors, the balance of the two types of attractions is reached either at the equator or more than 10 degrees away from the equator. The former case results in a single ITCZ over the equator and the latter case a double ITCZ straddling the equator.
    Keywords: Geophysics
    Type: American Meteorological Society 83rd Annual Meeting; Feb 09, 2003 - Feb 13, 2003; Long Beach, CA; United States
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    Goddard Cumulus Ensemble (GCE) Model: Application for Understanding Precipitation Processes (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: One of the most promising methods to test the representation of cloud processes used in climate models is to use observations together with Cloud Resolving Models (CRMs). The CRMs use more sophisticated and realistic representations of cloud microphysical processes, and they can reasonably well resolve the time evolution, structure, and life cycles of clouds and cloud systems (size about 2-200 km). The CRMs also allow explicit interaction between out-going longwave (cooling) and incoming solar (heating) radiation with clouds. Observations can provide the initial conditions and validation for CRM results. The Goddard Cumulus Ensemble (GCE) Model, a cloud-resolving model, has been developed and improved at NASA/Goddard Space Flight Center over the past two decades. Dr. Joanne Simpson played a central role in GCE modeling developments and applications. She was the lead author or co-author on more than forty GCE modeling papers. In this paper, a brief discussion and review of the application of the GCE model to (1) cloud interactions and mergers, (2) convective and stratiform interaction, (3) mechanisms of cloud-radiation interaction, (4) latent heating profiles and TRMM, and (5) responses of cloud systems to large-scale processes are provided. Comparisons between the GCE model's results, other cloud-resolving model results and observations are also examined.
    Keywords: Geophysics
    Type: 83rd AMS Meeting-Simpson Symposium; Feb 09, 2003 - Feb 13, 2003; Long Beach, CA; United States
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    HALOE Observations of Perturbations in High Northern Latitude NO and O3 During the April 2002 Solar Storm Episode (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The April 2002 solar storm event provides a unique opportunity to study the resulting effects on upper atmospheric constituents such as NO and O3. Two sources may perturb these constituents. For a magnetic-storm-source, energetic particles collide with and dissociate N2 in the lower thermosphere to produce excited nitrogen atoms which then combine with O to produce NO. The NO subsequently is transported down to lower altitudes where it reacts with and thus destroys mesospheric and possibly stratospheric ozone. For a solar-particle-event-source, high energy particles penetrate directly into the mesosphere, break apart N2 and water vapor, creating NOx and HOx to destroy ozone in the middle atmosphere. We present perturbations in high northern latitude NO and O3 as measured by the Halogen Occultation Experiment (HALOE) aboard the Upper Atmosphere Research Satellite between April 20-27. HALOE observations show an order of magnitude increase in mesospheric NO and a factor of approximately 2 decrease in mesospheric O3. We will also compare these observations with NASA GSFC 2D model computations.
    Keywords: Geophysics
    Type: American Geophysical Union Fall Meeting; Dec 06, 2002 - Dec 10, 2002; San Francisco, CA; United States
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    Middle Atmosphere Temperature Trends from Small Rocketsondes (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-18
    Description: Stratospheric temperature trends derived from United States meteorological rocketsonde measurements obtained between the late 1960's and mid 1990's are examined at the 50-, 40-, and 25-km altitude levels. Although the trends are different at each of the launch locations there is an unequivocal downward slope of about -0.1 K to -0.3K per year at many of the launch sites. Distances between launch sites and, in some cases unequal data-record lengths, inhibit determination of trend inter-relationship among the various sites. Although the data only provide a 'snapshot' of atmospheric behavior for the specific location, a particular advantage resulting from using these particular rocketsonde observations is their consistency over time. Thus, using the same rocketsonde type over the data period, i.e., Datasonde insures a significant reduction of instrument induced anomalies in the temperature profiles. Trends at the 25-km altitude level, approximately 30 hPa, are compared with trends from radiosonde observations. Both rocketsonde and radiosonde measurements were obtained at approximately the same local times and within less than 100 km of each other. Rocketsonde temperatures from the Former Soviet Union are also used and often complement trends from US data.
    Keywords: Geophysics
    Type: American Geophysical Union; Dec 06, 2002 - Dec 10, 2002; San Francisco, CA; United States
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    Propagation of Secondary Antiprotons and Cosmic Rays in the Galaxy (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Recent more accurate antiproton data obtained by the BESS team during the last solar minimum pose a challenge to conventional propagation models of cosmic rays. In particular, the diffusive reacceleration model, which matches well key secondary/primary isotope ratios in cosmic rays, fails to reproduce the secondary antiproton spectrum. Tuning both secondary/primary isotope ratios and antiprotons is possible, but requires artificial breaks in the diffusion coefficient and the injection spectrum of primaries. We will discuss some possibilities to overcome these difficulties in the propagation models. We will present new results of our calculation of CR propagation in the Galaxy using the GALPROP code.
    Keywords: Geophysics
    Type: LA-UR-02-2996
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    Microphysics, Radiation and Surface Processes in the Goddard Cumulus Ensemble (GCE) Model (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: In this talk, five specific major GCE improvements: (1) ice microphysics, (2) longwave and shortwave radiative transfer processes, (3) land surface processes, (4) ocean surface fluxes and (5) ocean mixed layer processes are presented. The performance of these new GCE improvements will be examined. Observations are used for model validation.
    Keywords: Geophysics
    Type: NASA Ames, Naval Post Graduate School and Naval Research Laboratory; Sep 15, 2002 - Sep 20, 2002; Monterery, CA; United States
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    Establishing A Geologic Baseline of Cape Canaveral''s Natural Landscape: Black Point Drive (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The goal of this project is to identify the process responsible for the formation of geomorphic features in the Black Point Drive area of Merritt Island National Wildlife Refuge/Kennedy Space Center (MINWR/KSC), northwest Cape Canaveral. This study confirms the principal landscape components (geomorphology) of Black Point Drive reflect interaction between surficial sediments deposited in association with late-Quaternary sea-level highstands and the chemical evolution of late-Cenozoic sub-surface limestone formations. The Black Point Drive landscape consists of an undulatory mesic terrain which dips westward into myriad circular and channel-like depression marshes and lakes. This geomorphic gradient may reflect: (1) spatial distinctions in the elevation, character or age of buried (pre-Miocene) limestone formations, (2) dissolution history of late-Quaternary coquina and/or (3) thickness of unconsolidated surface sediment. More detailed evaluation of subsurface data will be necessary before this uncertain0 can be resolved.
    Keywords: Geophysics
    Type: 2000 Final Administrative Report NASA/ASEE Summer Faculty Fellowship Program
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    Global Reference Atmospheric Model and Trace Constituents (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Global Reference Atmospheric Model (GRAM-99) is an engineering-level model of the Earth's atmosphere. It provides both mean values and perturbations for density, temperature, pressure, and winds, as well as monthly- and geographically-varying trace constituent concentrations. From 0-27 km, thermodynamics and winds are based on National Oceanic and Atmospheric Administration Global Upper Air Climatic Atlas (GUACA) climatology. Above 120 km, GRAM is based on the NASA Marshall Engineering Thermosphere (MET) model. In the intervening altitude region, GRAM is based on Middle Atmosphere Program (MAP) climatology that also forms the basis of the 1986 COSPAR Intemationa1 Reference Atmosphere (CIRA). MAP data in GRAM are augmented by a specially-derived longitude variation climatology. Atmospheric composition is represented in GRAM by concentrations of both major and minor species. Above 120 km, MET provides concentration values for N2, O2, Ar, O, He, and H. Below 120 km, species represented also include H2O, O3, N2O, CO, CH, and CO2. Water vapor in GRAM is based on a combination of GUACA, Air Force Geophysics Laboratory (AFGL), and NASA Langley Research Center climatologies. Other constituents below 120 km are based on a combination of AFGL and h4AP/CIRA climatologies. This report presents results of comparisons between GRAM Constituent concentrations and those provided by the Naval Research Laboratory (NRL) climatology of Summers (NRL,/MR/7641-93-7416, 1993). GRAM and NRL concentrations were compared for seven species (CH4, CO, CO2, H2O, N2O, O2, and O3) for months January, April, July, and October, over height range 0-115 km, and latitudes -90deg to + 90deg at 10deg increments. Average GRAM-NRL correlations range from 0.878 (for CO) to 0.975 (for O3), with an average over all seven species of 0.936 (standard deviation 0.049).
    Keywords: Geophysics
    Type: COSPAR 2002 World Space Congress; Oct 10, 2002 - Oct 19, 2002; Houston, TX; United States
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    Biogeochemistry of Microbial Mats (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The hierarchical organization of microbial ecosystems determines the rates of processes that shape Earth's environment, define the stage upon which major evolutionary events occurred, and create biosignatures in sediments and atmospheres. In cyanobacterial mats, oxygenic photosynthesis provides energy, organic substrates and oxygen to the ecosystem. Incident light changes with depth in the mat, both in intensity and spectral composition, and counteracting gradients of oxygen and sulfide shape the chemical microenvironment. A combination of benefits and hazards of light, oxygen and sulfide promotes the allocation of the various essential mat processes between light and dark periods and to various depths in the mat. Microliters produce hydrogen, small organic acids, nitrogen and sulfur species. Such compounds fuel a flow of energy and electrons in these ecosystems and thus shape interactions between groups of microorganisms. Coordinated observations of population distribution, abundance, and activity for an entire community are making fundamental questions in ecology accessible. These questions address those factors that sustain the remarkable diversity of microorganisms that are now being revealed by molecular techniques. These questions also target the processes that shape the various kinds of biosignatures that we will seek, both in ancient rocks from Earth and Mars, and in atmospheres of distant planets beyond our Solar System.
    Keywords: Geophysics
    Type: GeoBiology Summer 2002 Field Course; Jul 19, 2002 - Jul 27, 2002; Catalina Island, CA; United States
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    INTEX-NA: Intercontinental Chemical Transport Experiment - North America (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: INTEX-NA is an integrated atmospheric chemistry field experiment to be performed over North America using the NASA DC-8 and P-3B aircraft as its primary platforms. It seeks to understand the exchange of chemicals and aerosols between continents and the global troposphere. The constituents of interest are ozone and its precursors (hydrocarbons, NOX and HOX), aerosols, and the major greenhouse gases (CO2, CH4, N2O). INTEX-NA will provide the observational database needed to quantify inflow, outflow, and transformations of chemicals over North America. INTEX-NA is to be performed in two phases. Phase A will take place during the period of May-August 2004 and Phase B during March-June 2006. Phase A is in summer when photochemistry is most intense and climatic issues involving aerosols and carbon cycle are most pressing, and Phase B is in spring when Asian transport to North America is at its peak. INTEX-NA will coordinate its activities with concurrent measurement programs including satellites (e. g. Terra, Aura, Envisat), field activities undertaken by the North American Carbon Program (NACP), and other U.S. and international partners. However, it is being designed as a 'stand alone' mission such that its successful execution is not contingent on other programs. Synthesis of the ensemble of observation from surface, airborne, and space platforms, with the help of global/regional models is an important It is anticipated that approximately 175 flight hours for each of the aircraft (DC-8 and P-3B) will be required for each Phase. Principal operational sites are tentatively selected to be Bangor, ME; Wallops Island, VA; Seattle, WA; Rhinelander, WI; Lancaster, CA; and New Orleans, LA. These coastal and continental sites can support large missions and are suitable for INTEX-NA objectives. The experiment will be supported by forecasts from meteorological and chemical models, satellite observations, surface networks, and enhanced O3,-sonde releases. In addition to characterizing Atlantic-outflow and Pacific-inflow, INTEX-NA will characterize air masses transported between the U.S., Canada, and Mexico. INTEX-NA will be the first continental scale inflow, outflow, and transformation experiment to be performed over North America. It will provide the most comprehensive observational data set to date to understand the O3/NOX/HOX/aerosol photochemical system and the carbon cycle. One of the critical needs of the carbon cycle research is to obtain large-scale vertical and horizontal concentration gradients of CO2, throughout the troposphere over continental source/sink regions. INTEX-NA is ideally suited to perform this role. Coastal and continental operational sites will allow us to develop a curtain profile of greenhouse gases (e. g. CO2,) and other key pollutants across North America. Such information is central to our quantitative understanding of chemical budgets on the continental scale. We expect to provide a number of satellite under-flights over land and water to test and validate observations from the appropriate satellite platform (e. g. Aura). We plan to develop strong collaborations with other national and international observational programs. Results from INTEX-NA should directly benefit the development of environmental policy for air quality and climate change.
    Keywords: Geophysics
    Type: Scientific Workshop EXPORT-E2 (European Export of Precursors and Ozone by Long-Range Transport: EUROTRAC-2)/INTEX-NA; Unknown
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    The Living With a Star Geospace Investigations (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The Living With a Star Geospace Investigations is established to effectively address those phenomena the Geospace environment that directly affect life and society. The priority science questions focus on two broad areas: (1) ionospheric variability, especially at mid-latitudes, that affects navigation and communications and (2) the source, acceleration mechanisms, and sinks of the radiation belts that degrade satellite lifetimes, produce surface charging, and threaten manned space flight. Candidate missions to address these science foci will be presented as well as possible additional investigations and experiments that would enable an understanding of the Geospace at the system level.
    Keywords: Geophysics
    Type: 4th Oersted International Workshop; Sep 23, 2002 - Sep 27, 2002; Copenhagen; Denmark
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    Evolution of Ionospheric Convection during a Double Transpolar Arc Phenomenon on February 11, 1999 (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: An evolution of ionospheric convection was studied for a double transpolar arc phenomenon on February 11, 1999. While one transpolar arc split from the auroral oval in the morning sector and drifted duskward, another arc appeared in the evening sector. The convection was investigated with three velocity data sets: E B drift velocities from the ASTRID-2 satellite; Ion Driftmeter data from the DMSP satellites; and Doppler-shift data from the Super-DARN radars. We inferred convection cells from these data sets and found that the number of convection cells changed from three to four as the dominance of IMF changed from a negative By to a positive Bz. Our result suggests that the ionospheric convection that has been so far discussed for various conditions of IMF may be applied even to the cases accompanied by transpolar arcs.
    Keywords: Geophysics
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    Self-Consistent Magnetosphere-Ionosphere Coupling and Associated Plasma Energization Processes (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Magnetosphere-Ionosphere (MI) coupling and associated with this process electron and ion energization processes have interested scientists for decades and, in spite of experimental and theoretical research efforts, are still ones of the least well known dynamic processes in space plasma physics. The reason for this is that the numerous physical processes associated with MI coupling occur over multiple spatial lengths and temporal scales. One typical example of MI coupling is large scale ring current (RC) electrodynamic coupling that includes calculation of the magnetospheric electric field that is consistent with the ring current (RC) distribution. A general scheme for numerical simulation of such large-scale magnetosphere-ionosphere coupling processes has been presented earlier in many works. The mathematical formulation of these models are based on "modified frozen-in flux theorem" for an ensemble of adiabatically drifting particles in the magnetosphere. By tracking the flow of particles through the inner magnetosphere, the bounce-averaged phase space density of the hot ions and electrons can be reconstructed and the magnetospheric electric field can be calculated such that it is consistent with the particle distribution in the magnetosphere. The new a self-consistent ring current model has been developed that couples electron and ion magnetospheric dynamics with calculation of electric field. Two new features were taken into account in addition to the RC ions, we solve an electron kinetic equation in our model, self-consistently including these results in the solution. Second, using different analytical relationships, we calculate the height integrated ionospheric conductances as the function of precipitated high energy magnetospheric electrons and ions as produced by our model. This results in fundamental changes to the electric potential pattern in the inner magnetosphere, with a smaller Alfven boundary than previous potential formulations would predict but one consistent with recent satellite observations. This leads to deeper penetration of the plasma sheet ions and electrons into the inner magnetosphere and more effective ring current ions and electron energization.
    Keywords: Geophysics
    Type: Astrophysical Particle Acceleration in Geospace and Beyond; Oct 06, 2002 - Oct 10, 2002; Chattanooga, TN; United States
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    ALTUS Cumulus Electrification Study (ACES) (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The ALTUS Cumulus Electrification Study (ACES) is an uninhabited aerial vehicle (UAV)-based project that will investigate thunderstorms in the vicinity of the Florida Everglades in August 2002. ACES is being conducted to both investigate storm electrical activity and its relationship to storm morphology, and validate Tropical Rainfall Measurement Mission (TRMM) satellite measurements. In addition, as part of NASA's UAV-based science demonstration program, this project will provide a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. Part of the demonstration involves getting approvals from the Federal Aviation Administration and the NASA airworthiness flight safety review board. ACES will employ the ALTUS II aircraft, built by General Atomics - Aeronautical Systems, Inc. Key science objectives simultaneously addressed by ACES are to: (1) investigate lightning-storm relationships, (2) study storm electrical budgets, and (3) provide Lightning Imaging Sensor validation. The ACES payload, already developed and flown on ALTUS, includes electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. ACES will contribute important electrical and optical measurements not available from other sources. Also, the high altitude vantage point of the UAV observing platform (up to 55,000 feet) offers a useful 'cloud-top' perspective. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high altitude flight, the ALTUS will be flown near, and when possible, above (but never into) thunderstorms for long periods of time, allowing investigations to be conducted over entire storm life cycles. In addition, concurrent ground-based observations will enable the UAV measurements to be more completely interpreted and evaluated in the context of the thunderstorm structure, evolution, and environment.
    Keywords: Geophysics
    Type: Technical Analysis and Applications Center Conference; Oct 28, 2002 - Oct 30, 2002; Santa Fe, NM; United States
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    Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. Several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer (TTL). Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the TTL can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, a Lagrangian, one-dimensional cloud model has been used to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the TTL. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth, advection, and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties and cloud frequencies depend strongly on the assumed supersaturation threshold for ice nucleation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is 10-50% larger than the saturation mixing ratio. I will also discuss the impacts of Kelvin waves and gravity waves on cloud properties and dehydration efficiency. These simulations can be used to determine whether observed lower stratospheric water vapor mixing ratios can be explained by dehydration associated with in situ TTL cloud formation alone.
    Keywords: Geophysics
    Type: American Meteorological Society Middle Atmosphere Meeting; Unknown
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    Plasmasphere Empirical Modeling with the IMAGE Mission (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Empirical models of plasmaspheric properties date from the pioneering work of Storey where he developed the analysis of ground whistler observations that lead to his estimate for the equatorial plasma density at L=3. The most recent in situ satellite study takes us to 1000 CRRES satellite passes and a statistical analysis of the plasmapause location at all local times and for varying geomagnetic conditions by Moldwin et al. These and many other studies over the intervening 49 years have given us a strong familiarity with the distribution of cold plasmaspheric ions throughout the magnetosphere. The major components of inner plasmasphere, nightside bulge, sunward convection tail, and plasmapause are all well established. Storm-time erosion and the resulting ionospheric refilling has been encompassed, even if not completely understood. Small-scale density variations near the plasmapause and extending at least to geosynchronous orbit have been characterized in a variety of ways, even though we do not yet understand their origin. This paper will present early empirical modeling results from the inversion of IMAGE/EW global intensity images to density distributions. Densities are obtained in this initial study through use of forward image modeling with a simple 3-parameter plasmaspheric and plasmapause mathematical model. Individual interior plasmaspheric density profiles and plasmapause locations are obtained every 10 degrees in magnetic local time for each E W image analyzed. Derived profile parameters are statistically characterized in the context of storm magnitude and evolution. Identified patterns in the appearance of plasmaspheric structures, plasmapause erosion, and refilling will be presented. Comparisons to existing empirical plasmaspheric models and the implications for new modeling will be presented. Additional information is included in the original extended abstract.
    Keywords: Geophysics
    Type: XXVIIth General Assembly of the International Union of Radio Science; Aug 17, 2002 - Aug 24, 2002; Maastricht; Netherlands
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    Clouds in the Winter Arctic Tropopause Region (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Water vapor in the winter arctic tropopause region is important because, after the tropical tropopause region, the winter arctic tropopause has the coldest temperatures in the tropospheric northern hemisphere. This suggests the potential for cloud formation that can remove water vapor from a part of the atmosphere where radiatively active gases (such as water) exert a disproportionate influence on the earth's radiation budget. Previous work by the same authors has shown that this cloud formation extends into the stratosphere, with 20% of the parcels having ozone values of 300-350 ppbv experiencing ice saturation in any given 10 day period period during the late winter. In fact, temperatures are cold enough that 5-10% of the parcels experience saturation even if the water content is below the prevailing stratospheric value of 5 ppmv. This work describes a case study of clouds observed by aircraft near the winter arctic tropopause during the SAGE Ozone Loss and Validation Experiment (SOLVE). This provided a unique opportunity to examine dehydration processes in this region since in situ water, tracer, cloud particle, and meteorological data were all available simultaneously. During this period, temperatures were cold enough at the tropopause to produce saturation mixing ratios of 3-4 ppmv. Thus, clouds were actually observed within the stratosphere. Back trajectories indicate that the air in these clouds came from lower latitudes and altitudes. The study describes the nature of the clouds, the history of the air, and the possible implications for the upper tropospheric water budget.
    Keywords: Geophysics
    Type: American Meteorological Society''s 12th Conference on Middle Atmosphere; Nov 04, 2002 - Nov 07, 2002; San Antonio, TX; United States
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    Development and Implementation of an Empirical Ionosphere Variability Model (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Spacecraft designers and operations support personnel involved in space environment analysis for low Earth orbit missions require ionospheric specification and forecast models that provide not only average ionospheric plasma parameters for a given set of geophysical conditions but the statistical variations about the mean as well. This presentation describes the development of a prototype empirical model intended for use with the International Reference Ionosphere (IRI) to provide ionospheric Ne and Te variability. We first describe the database of on-orbit observations from a variety of spacecraft and ground based radars over a wide range of latitudes and altitudes used to obtain estimates of the environment variability. Next, comparison of the observations with the IRI model provide estimates of the deviations from the average model as well as the range of possible values that may correspond to a given IRI output. Options for implementation of the statistical variations in software that can be run with the IRI model are described. Finally, we provide example applications including thrust estimates for tethered satellites and specification of sunrise Ne, Te conditions required to support spacecraft charging issues for satellites with high voltage solar arrays.
    Keywords: Geophysics
    Type: 34th COSPAR Sessions World Space Conference; Oct 10, 2002 - Oct 19, 2002; Houston, TX; United States
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    On the Tropospheric Measurements of Ozone by the Stratospheric Aerosol and Gas Experiment II (SAGE II, version 6.1) in the Tropics (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Tropospheric measurements of ozone from SAGE II (version 6.1) in the tropics have been analyzed using 12 years of data (1985-1990, 1994-1999). The seasonally averaged vertical profiles of the ozone mixing ratio in the upper troposphere have been presented for the first time from satellite measurements. These profiles show qualitative similarities with corresponding seasonal mean ozonesonde profiles at northern and southern tropical stations and are about 40-50% less than the sonde values. Despite this systematic offset, the measurements appear to be consistent with a zonal wave one pattern in the upper tropospheric column ozone and with the recently predicted summertime ozone enhancement over the Middle East. These results thus affirm the usefulness of the occultation method in studying tropospheric ozone.
    Keywords: Geophysics
    Type: SAGE II Ozone Analysis; G35-610
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    Long-Term Properties of Accretion Discs in X-ray Binaries (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Long term X-ray monitoring data from the RXTE All Sky Monitor (ASM) reveal that the third (superorbital) period in SMC X-1 is not constant but varies between 40-60 days. A dynamic power spectrum analysis indicates that the third period has been present continuously throughout the five years of ASM observations. This period changed smoothly from 60 days to 45 days and then returned to its former value, on a timescale of approximately 1600 days. During the nearly 4 years of overlap between the CGRO & RXTE missions, the simultaneous BATSE hard X-ray data confirm this variation in SMC X-1. Sources of systematic error and possible artefacts are investigated and found to be incapable of reproducing the results reported here. Our disco cry of such an instability in the superorbital period of SMC X-1 is interpreted in the context of recent theoretical studies of warped, precessing accretion discs. We find that the behaviour of SMC X-1 is consistent with a radiation - driven warping model.
    Keywords: Geophysics
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    Overview of the Upper Atmosphere Research Satellite: Observations from 1991 to 2002 (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The Upper Atmosphere Research Satellite (UARS) was launched in September 1991 by the Space Shuttle Discovery. Seven of the original ten instruments aboard the UARS are functional and six instruments regularly take measurements. The UARS is in a stable observing configuration, in spite of experiencing several anomalies which have impacted the data tape storage and power available. Power sharing and "real-time" operations using the Tracking and Data Relay Satellites have reduced the data collection over the past five years. Although the UARS measurements have not been continuous, the UARS instruments HALOE, SUSIM, SOLSTICE, HRDI, WINDII, and PEM have provided important observations over an entire solar cycle. The UARS HALOE instrument measures ozone and other constituents important in understanding ozone variations. The UARS SUSIM and SOLSTICE instruments observe ultraviolet light between 120 and 420 nm, which influence middle atmospheric constituent fluctuations. The UARS HRDI and WINDII instruments measure winds in the stratosphere, mesosphere, and thermosphere, which move constituents among the various atmospheric regions. The UARS PEM instrument provides observations of input precipitating charged particles, including both electrons and protons. This paper will provide an overview about the UARS mission and its relevant atmospheric measurements.
    Keywords: Geophysics
    Type: 34th COSPAR Scientific Assembly/2nd World Space Congress; Oct 10, 2002 - Oct 19, 2002; Houston, TX; United States
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    Measurements of Oxygenated Organic Chemicals In the Pacific Troposphere During TRACE-P: Higher Aldehydes (less than C(sub 1)), Their Sources, and Potential Role In Atmospheric Oxidation (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Airborne measurements of a large number of oxygenated organics were carried out in the Pacific troposphere (to 12 km) in the Spring of 2001 (Feb. 24-April 10). Specifically these measurements included acetaldehyde, propanaldehyde, acetone, methylethyl ketone, methanol, ethanol, PAM and organic nitrates. Independent measurements of formaldehyde, peroxides, and tracers were also available. Highly polluted as well as pristine air masses were sampled. Oxygenated organics were abundant in the clean In troposphere and were greatly enhanced in the outflow regions from Asia. Extremely high concentrations of aldehydes could be measured in the troposphere. It is not possible to explain the large abundances of aldehydes in the background troposphere without invoking significant oceanic sources. A strong correlation between the observed mixing ratios of formaldehyde and acetaldehyde is present. We infer that higher aldehydes (such as acetaldehyde and propanaldehyde) may provide a large source of formaldehyde and sequester Cox throughout the troposphere. The atmospheric behavior of acetone, methylethyl ketone, and methanol is generally indicative of their common terrestrial sources with a Image contribution from biomass/biofuel burning. A vast body of data has been collected and it is being analyzed both statistically and with the help of models to better understand the role that oxygenated organics play in the atmosphere and to unravel their sources and sinks. These results will be presented.
    Keywords: Geophysics
    Type: 7th Scientific Conference of the International Global Atmospheric Chemistry Project; Sep 18, 2002 - Sep 25, 2002; Crete; Greece
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    In-Situ Measurements of HCN and CH3CN in the Pacific Troposphere: Sources, Sinks, and Comparisons with Spectroscopic Observations (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: We report the first in-situ measurements of hydrogen cyanide (HCN) and acetonitrile (CH3CN) from the Pacific troposphere (0-12 km) obtained during the NASA/Trace-P mission (Feb.-April, 2001). Mean HCN and CH3CN mixing ratios of 243 (+/-118) ppt and 149 (+/-56) ppt respectively, were measured. The in-situ observations correspond to a total HCN column of 4.4-4.9 x 10(exp 15) molec. cm(exp -2) and a CH3CN column of 2.8-3.0 x 10(exp 15) molec. cm(exp -2). This HCN column is in good agreement with available spectroscopic observations. The atmospheric concentrations of HCN and CH3CN were greatly influenced by outflow of pollution from Asia. There is a linear relationship between the mixing ratios of HCN and CH3CN, and in turn these are well correlated with tracers of biomass combustion (e.g. CH3Cl, CO). Relative enhancements with respect to known tracers of biomass combustion within selected plumes in the free troposphere, and pollution episodes in the boundary layer allow an estimation of a global biomass burning source of 0.8+/-0.4 Tg (N)/y for HCN and 0.4+/-0.1 Tg (N)/y for CH3CN. In comparison, emissions from automobiles and industry are quite small (〈0.05 Tg (N)/y). The vertical structure of HCN and CH3CN indicated reduced mixing ratios in the MBL (Marine Boundary Layer). Using, a simple box model, the observed gradients across the top of the MBL are used to derive an oceanic flux of 6.7 x 10(exp -15) g (N) cm(exp -2)/s for HCN and 4.8 x 10(exp -15) g (N) cm(exp -2)/s for CH3CN. An air-sea exchange model is used to conclude that this flux can be maintained if the oceans are under-saturated in HCN and CH3CN by 23% and 17%, respectively. It is inferred that oceanic loss is a dominant sink for these nitrites, and they deposit some 1.3 Tg (N) of nitrogen annually to the oceans. Assuming reaction with OH radicals and loss to the oceans as the major removal processes, a mean atmospheric residence time of 4.7 months for HCN and 5.1 months for CH3CN is calculated. A global budget analysis shows that the sources and sinks of HCN and CH3CN are roughly in balance. There are indications that biogenic sources may also be present. Mechanisms involved in nitrate formation during combustion and removal in the oceans are poorly understood.
    Keywords: Geophysics
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  • 92
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    Cross Scale Coupling of Alfven Turbulence in the Polar Wind Region (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Ionosphere-magnetosphere coupling phenomena are extremely complex and diverse, involving a whole series of processes operating over a wide range of spatial and temporal scales. One of the fundamental aspects of understanding this coupling is the polar wind, which is a dominant mechanism of mass transport from the ionospheric source region to the magnetosphere and strongly influences the plasma parameters above the F2 density peak. The combined effects of photoelectrons, and the ponderomotive force will be presented based on our polar wind model. The presence of photoelectrons and low frequency oscillations (that create the ponderomotive force) increase ion outflows. It is also demonstrated that large-amplitude low-frequency waves (LFW) may generate lower hybrid waves (LHW) in the auroral zone. The excitation of LHW by a LF wave may lead to the appearance of an additional channel of energy transfer from, for example, Alfven or fast magnetosonic waves, to particles. This process then influences the formation of the plasma distribution function at the expense of acceleration in the tail of the distribution during the collapse of the LHW. The ion energization due to the LHW can be comparable with that produced by the ponderomotive force of the LFW.
    Keywords: Geophysics
    Type: EGS General Assembly; Apr 01, 2002; Nice; France
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  • 93
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    IMAGE EUV and RPI Derived Distributions of Plasmaspheric Plasma and Plasmaspheric Modeling (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The global modeling of plasmaspheric plasma has remained fairly rudimentary over the last 30-years, owing to our limited ability to validate model results experimentally. The realization that voids and filamentary structures covering a range of scales sizes are formed in the distribution of thermal plasma has only been possible with global imaging and enables entirely new advances in modeling the near Earth space environment. Advances in modeling in the context of these new observations will be presented and discussed.
    Keywords: Geophysics
    Type: Magnetospheric Imaging Workshop; Feb 05, 2002 - Feb 08, 2002; Yosemite National Park, CA; United States
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    Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (i) the rarefaction shocks, (ii) the discontinuities in the potential distributions, and (iii) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains two electron populations, the temporal evolution of the potential and the plasma. distribution generates evolving multiple double layers with an extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature.
    Keywords: Geophysics
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  • 95
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    Phosphorus Equilibria Among Mafic Silicate Phases (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet 〉 olivine 〉 orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The data also indicate that DXVliQP2O5 decrease in the same order, but DOVLiQP2O5 and DOpx/LiQP205 are likely constant, respectively equal to 0.08(3) and 0.007(4), in contrast, DG1ILiQP205 increases from 0.15(3) to 0.36(10) as garnet becomes majoritic, thus silica-enriched, and may also depend on liquid composition (SiO2, P2O5 and Na2O wt%).
    Keywords: Geophysics
    Type: JSC-CN-21204 , 2002 Denver Annual Meeting; Oct 27, 2002 - Oct 30, 2002; Denver, CO; United States
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    The Global Geophysical Fluids Center of IERS (and its Special Bureau for Mantle) (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The Global Geophysical Fluids Center (GGFC) was established by the International Earth Rotation Service (IERS) on IERS's 10th anniversary day January 1, 1998, in an effort to expand IERS's services to the scientific community. Under the GGFC, eight Special Bureaus (SB) have been selected, each to be responsible for research and data service activities pertaining to mass transports and related geophysical processes in specific components of the Earth system, or "global geophysical fluids," including the atmosphere, oceans, solid Earth, core, and geophysical processes of gravity, loading, tides and hydrological cycles. GGFC and the SBs have the responsibility of supporting, facilitating, and providing services to the worldwide research community, in areas related to the variations in Earth rotation, gravity field and geocenter that are caused by mass transport in the global geophysical fluids. These minute variations have been observed by various space geodetic techniques, as effective remote sensing tools, with ever increasing precision/accuracy and temporal/spatial resolution. The GGFC and SBs have organized dedicated workshops and special sessions at international conferences, published articles, and held regular business meetings. The SBs also maintain individual website for data services and information exchanges. See URL 〈bowie.gsfc.nasa.gov/ggfc/〉. In particular, the SB for Mantle focuses on large-scale mass redistributions that occur in the mantle in association with various dynamic processes, including seismic activities, the post-glacial rebound, and mantle convections.
    Keywords: Geophysics
    Type: American Geophysical Union Meeting; Dec 06, 2002 - Dec 10, 2002; San Francisco, CA; United States
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    Gravity Fields from CHAMP Mission Data (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The CHAMP mission, launched in July 2000, is the first in a series of missions that will revolutionize our ability to model the Earth s geopotential. The CHAMP spacecraft is equipped for precision tracking by the Global Positioning System (GPS) and Satellite Laser Ranging (SLR) along with a precision accelerometer to provide measurements of the surface forces. Preliminary satellite-only geopotential solutions with only 30 days of CHAMP data are, by some criteria, as strong as solutions made from tracking data collected over the previous 30 years of the space age. Compared to EGM96, CHAMP makes notable contributions in regions where the terrestrial data (surface gravimetry and altimetry) were weak, for example in the polar regions, in the Amazon and the Himalayas. The CHAMP data allow us to separate the geoid from the dynamic ocean topography (DOT) up to at least degree 25 rather than just under degree 20 as in EGM96. We report on satellite-only and combination models that incorporate up to 100 days of CHAMP data as well as other satellite data. We report on our updated processing of the CHAMP tracking and accelerometer data and evaluate the performance of the geopotential models using a variety of tests.
    Keywords: Geophysics
    Type: American Geophysical Union Meeting; Dec 06, 2002 - Dec 10, 2002; San Francisco, CA; United States
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    Observations of Overshooting Convective Tops and Dynamical Implications (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Convective tops overshooting the tropopause have been suggested in the literature to play an important role in modifying the tropical tropopause. The structure of thunderstorm tops overshooting the tropopause have been difficult to measure due to the intensity of the convection and aircraft safety. This paper presents remote observations of overshooting convective tops with the high-altitude ER-2 aircraft during several of the Tropical Rain Measuring Mission (TRMM) and (Convection and Moisture Experiment) CAMEX campaigns. The ER-2 was instrumented with the down-looking ER-2 Doppler Radar (EDOP), a new dropsonde system (ER-2 High Altitude Dropsonde, EHAD), and an IR radiometer (Modis Airborne Simulator, MAS). Measurements were collected in Florida and Amazonia (Brazil). In this study, we utilize the radar cloud top information and cloud top infrared temperatures to document the amount of overshoot and temperature difference relative to the soundings provided by dropsondes and conventional upsondes. The radar measurements provide the details of the updraft structure near cloud top, and it is found that tops of stronger convective cells can overshoot by 1-2 km and with temperatures 5C colder than the tropopause minimum temperature. The negatively buoyant cloud tops are also evidenced in the Doppler measurements by strong subsiding flow along the sides of the convective tops . These findings support some of the conceptual and modeling studies of deep convection penetrating the tropopause.
    Keywords: Geophysics
    Type: American Geophysical Union Spring Meeting; May 28, 2002 - May 31, 2002; Washington, DC; United States
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    TRMM Radar Observations of Cloud Tops in the Tropical Tropopause Layer (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Air dehydrates to stratospheric abundances in the tropical tropopause layer (TTL). The role of overshooting convection in the dehydration process is not well understood. To study this effect, we use the TRMM (Tropical Rainfall Measuring Mission) precipitation radar (PR) to measure the altitudes of cloud tops forming in the TTL. Because the radar signal is dominated by scatter from large particles, these cloud observations imply the presence of strong convective systems with large updraft. Both winter and summer data from two different years are examined to study both interseasonal and interannual variability. The global distribution of these clouds is in good agreement with those of the surface precipitation rates. In addition, the altitude distributions of these clouds follow an exponential dependence. However, clouds over continental regions typically extend to higher altitudes in the tropics. Almost no cloud tops were observed above 20 km. Comparison between the radar cloud tops and colocated IR brightness temperature measurements reveal a large difference in both the diurnal cycle and intensity between continental and oceanic convection.
    Keywords: Geophysics
    Type: 2002 Spring AGU Meeting; May 28, 2002 - May 31, 2002; Washington, DC; United States
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    Ring Current Ion Coupling with Electromagnetic Ion Cyclotron Waves (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: A new ring current global model has been developed that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes wave evolution of electromagnetic ion cyclotron waves (EMIC). The coupled model is able to simulate, for the first time self-consistently calculated RC ion kinetic and evolution of EMIC waves that propagate along geomagnetic field lines and reflect from the ionosphere. Ionospheric properties affect the reflection index through the integral Pedersen and Hall conductivities. The structure and dynamics of the ring current proton precipitating flux regions, intensities of EMIC global RC energy balance, and some other parameters will be studied in detail for the selected geomagnetic storms.
    Keywords: Geophysics
    Type: Spring AGU; 28-31 May 202; Washington, DC; United States
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