ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Call number: AWI A14-00-0235
    Type of Medium: Monograph available for loan
    Pages: o. S.-zählg.
    Series Statement: IPSL Publication
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1573-1472
    Keywords: Unstable atmospheric boundary layer ; Entrainment zone ; Turbulent kinetic energy shear production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The thickness of the entrainment zone at the top of the marine atmosphericboundary layer (MABL) has been documented by an airborne lidar on twoconsecutive days during a cold-air outbreak episode over the Mediterranean.In addition to the lidar observations, in situ turbulent flux measurementsat three levels in the MABL were made by a second aircraft. The flights' tracksare broken down in segments 25–30 km long and the data are filtered for theparametrization of turbulent entrainment in the MABL at scales smaller thana few kilometres. The structural parameters of the entrainment zone aredetermined by lidar from the distributions of the instantaneous MABL topheight. The average values Ph0 and Ph2 of the cumulativeprobability distributions are used to define the bottom and top heights of the entrainment zone h0 and h2, respectively. The parameters h0 andh2 are calculated by reference to a linear vertical buoyancy flux profilein the framework of a first-order jump model. The model is constrained by bothlidar and in situ data to determine Ph0 and Ph2 and so h0and h2. In unstable conditions theaverage fraction Ph0 is estimated to be 6.0 ± 1%. It is shown to beslightly sensitive to the presence of cloud at small cloud fractions.The mean value of the ratio of the inversion level buoyancy flux to the surfacebuoyancy flux ARv is found to range from 0.15 to 0.30 depending on the shearin the MABL. The average value is 0.22 ± 0.05. Our resultsare in good agreement with previous analysis at comparable spatial scales.In purely convective conditions, the value of ARv given by theparametrizations fitted to our results is about 0.10–0.12, a value smallerthan the commonly accepted value of 0.2. When compared to previousparametrization results, our proportionality constant for the mechanicalproduction of turbulent kinetic energy is also found to be scaled down, ingood agreement with large-eddy simulation results. It is suggestedthat mesoscale organized motions in the MABL is the source of thisdifference.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-1472
    Keywords: Heterodyne Doppler lidar ; Organized large eddies ; Planetary boundary laye ; Turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In an experiment investigating the planetary boundary layer (PBL) wind and temperature fields, and PBL inversion height recorded by various instruments, the results reveal the presence of organized large eddies (OLE) or rolls. The measurements by lidars, anemometers, soundings and sodar gave an overview of the characteristics of the rolls and sources of energy production that maintain them. The experimental results obtained on two consecutive days are compared to model outputs. The agreement is excellent, showing that thermal stratification and wind shear are important factors in the structure and dynamics of OLE. A heterodyne Doppler lidar (HDL) is shown to be a useful tool in the study of OLE.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-1472
    Keywords: Boundary-layer model ; Mixed-layer dynamics ; Organized large eddies ; Ekman flow ; Cold-air outbreak
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The internal thermal boundary layer developing over the Mediterranean during a cold-air outbreak associated with a Tramontane event has been studied by means of airborne lidar, in situ sensors, and a modelling approach that consisted of nesting the University of Washington (UW) planetary boundary-layer (PBL) model in an advective zero-order jump model. This approach bypasses some of the deficiencies associated with each model: the absence of the dynamics in the mixed layer for the zero-order jump model and the lack of an inversion at the PBL top for the UW PBL model. Particular attention is given to the parameterization of the entrainment flux at the PBL top. Values of the entrainment closure parameter derived with the model when matching PBL structure observations are much lower than those derived with standard zero-order jump models. They also are in good agreement with values measured in different meteorological situations by other studies. This improvement is a result of the introduction of turbulent kinetic energy production in the mixed layer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1573-1472
    Keywords: Surface layer ; Roughness length ; Sonic anemometer ; Column modelling ; Urban area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Atmospheric boundary layer (ABL) turbulent processes in the Paris area have been documented in the framework of the étude de la Couche Limite en Agglomération Parisienne (ECLAP). Under anticyclonic conditions, simulations are made with a ‘column’ modelling approach, based on the three-dimensional version of the non-hydrostatic mesoscale model MERCURE restricted to a small domain. This ‘column’ model uses existing state-of-the-art surface-layer parameterizations (the addition of the convective velocity scale to the mean wind speed in near free convection periods, the prescription of the effective dynamical roughness length as well as a differentiation between dynamical and thermal roughness lengths). To ensure the representativeness of the comparison between measurements and simulations, the dynamical and thermal effective roughness lengths characterizing the experimental site are prescribed explicitly in the model, using sonic anemometer measurements. We show that the parameterizations implemented in MERCURE for this study enable a good description, by the three-dimensional model, of the observed complex ABL dynamics. We also show that in the region of Paris, the synoptic scale and mesoscale dynamics can have a dramatic impact on the ABL dynamics and turbulent processes at the local scale. This study is a first attempt at improving our ability to predict meteorological factors affecting urban air quality.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2019-07-13
    Description: CALIPSO will carry the first polarization lidar in orbit, along with infrared and visible passive imagers, and will fly in formation as part of the Afternoon Constellation (A-train). The acquisition of observations which are simultaneous and coincident with observations from other instruments of the A-train will allow numerous synergies to be realized from combining CALIPSO observations with observations from other platforms. In particular, cloud observations from the CALIPSO lidar and the CloudSat radar will complement each other, together encompassing the variety of clouds found in the atmosphere, from thin cirrus to deep convective clouds. CALIPSO has been developed within the framework of a collaboration between NASA and CNES and is currently scheduled to launch, along with the CloudSat satellite, in spring 2006. This paper will present an overview of the CALIPSO mission, including initial results.
    Keywords: Meteorology and Climatology
    Type: 23rd International Laser Radar Conference (ILRC23); 24-28 Jul. 2006; Nara; Japan
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2019-07-10
    Description: In couple of years we expect the launch of the CALIPSO lidar spaceborne mission designed to observe aerosols and clouds. CALIPSO will collect profiles of the lidar attenuated backscattering coefficients in two spectral wavelengths (0.53 and 1.06 microns). Observations are provided along the track of the satellite around the globe from pole to pole. The attenuated backscattering coefficients are sensitive to the vertical distribution of aerosol particles, their shape and size. However the information is insufficient to be mapped into unique aerosol physical properties and vertical distribution. Infinite number of physical solutions can reconstruct the same two wavelength backscattered profile measured from space. CALIPSO will fly in formation with the Aqua satellite and the MODIS spectro-radiometer on board. Spectral radiances measured by MODIS in six channels between 0.55 and 2.13 microns simultaneously with the CALIPSO observations can constrain the solutions and resolve this ambiguity, albeit under some assumptions. In this paper we describe the inversion method and apply it to aircraft lidar and MODIS data collected over a dust storm off the coast of West Africa during the SHADE experiment. It is shown that the product of the single scattering albedo, omega, and the phase function, P, for backscattering can be retrieved from the synergism between measurements avoiding a priori hypotheses required for inverting lidar measurements alone. The resultant value of (omega)P(180 deg.) = 0.016/sr are significantly different from what is expected using Mie theory, but are in good agreement with recent results obtained from lidar observations of dust episodes. The inversion is robust in the presence of noise of 10% and 20% in the lidar signal in the 0.53 and 1.06 pm channels respectively. Calibration errors of the lidar of 5 to 10% can cause an error in optical thickness of 20 to 40% respectively in the tested cases. The lidar calibration errors cause degradation in the ability to fit the MODIS data. Therefore the MODIS measurements can be used to identify the calibration problem and correct for it. The CALIPSO-MODIS measurements of the profiles of fine and coarse aerosols, together with CALIPSO measurements of clouds vertical distribution, is expected to be critically important in understanding aerosol transport across continents and political boundaries, and to study aerosol-cloud interaction and its effect on precipitation and global forcing of climate.
    Keywords: Earth Resources and Remote Sensing
    Type: TGRS-00230-2002
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2019-07-13
    Description: A new approach has been proposed to determine ocean subsurface particulate backscattering coefficient bbp from CALIOP 30deg off-nadir lidar measurements. The new method also provides estimates of the particle volume scattering function at the 180deg scattering angle. The CALIOP based layer-integrated lidar backscatter and particulate backscattering coefficients are compared with the results obtained from MODIS ocean color measurements. The comparison analysis shows that ocean subsurface lidar backscatter and particulate backscattering coefficient bbp can be accurately obtained from CALIOP lidar measurements, thereby supporting the use of space-borne lidar measurements for ocean subsurface studies.
    Keywords: Earth Resources and Remote Sensing; Oceanography
    Type: NF1676L-25398 , Journal of Optics Express (e-ISSN 1094-4087); 24; 25; 29001-29008
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2019-07-13
    Description: We have been studying the backscatter ratio of the two CALIPSO wavelengths for 3 different targets. We are showing the ratio of integrate attenuated backscatter coefficient for cirrus clouds, ocean surface and liquid. Water clouds for one month of nightime data (left:July,right:December), Only opaque cirrus classified as randomly oriented ice[1] are used. For ocean and water clouds, only the clearest shots, determined by a threshold on integrated attenuated backscatter are used. Two things can be immediately observed: 1. A similar trend (black dotted line) is visible using all targets, the color ratio shows a tendency to be higher north and lower south for those two months. 2. The water clouds average value is around 15% lower than ocean surface and cirrus clouds. This is due to the different multiple scattering at 532 nm and 1064 nm [2] which strongly impact the water cloud retrieval. Conclusion: Different targets can be used to improve CALIPSO 1064 nm calibration accuracy. All of them show the signature of an instrumental calibration shift. Multiple scattering introduce a bias in liquid water cloud signal but it still compares very well with all other methods and should not be overlooked. The effect of multiple scattering in liquid and ice clouds will be the subject of future research. If there really is a sampling issue. Combining all methods to increase the sampling, mapping the calibration coefficient or trying to reach an orbit per orbit calibration seems an appropriate way.
    Keywords: Communications and Radar
    Type: NF1676L-11600 , International Symposium on the A-Train Satellite Constellation 2010; 25-28 Oct. 2010; New Orleans, LA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2019-07-13
    Description: We are demonstrating on a few cases the capability of CALIPSO to retrieve the 532 nm lidar ratio over the ocean when CloudSat surface scattering cross section is used as a constraint. We are presenting the algorithm used and comparisons with the column lidar ratio retrieved by the NASA airborne high spectral resolution lidar. For the three cases presented here, the agreement is fairly good. The average CALIPSO 532 nm column lidar ratio bias is 13.7% relative to HSRL, and the relative standard deviation is 13.6%. Considering the natural variability of aerosol microphysical properties, this level of accuracy is significant since the lidar ratio is a good indicator of aerosol types. We are discussing dependencies of the accuracy of retrieved aerosol lidar ratio on atmospheric aerosol homogeneity, lidar signal to noise ratio, and errors in the optical depth retrievals. We are obtaining the best result (bias 7% and standard deviation around 6%) for a nighttime case with a relatively constant lidar ratio (in the vertical) indicative of homogeneous aerosol type
    Keywords: Optics
    Type: NF1676L-13531 , Optics Express; 19; 29; 18696-18706
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...