ALBERT

Description: The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.

Description: Satellite scatterometers are active microwave radars designed to yield measurements of near surface horizontal wind velocity over the ocean. Scatterometers are unique in that they are the only existing microwave remote sensing instruments that allow measurements of both wind speed and wind direction. NASA will fly a scatterometer, NSCAT, aboard the Navy Ocean Remote Sensing System (N-ROSS) mission starting in late 1990. N-ROSS is a spaceborne ocean remote sensing system with a planned mission life of three years. In addition to the NSCAT, N-ROSS will have three other microwave instruments mounted on a single satellite flying in a near polar orbit: an altimeter; a special sensor microwave/imager (SSM/I); and a low frequency microwave radiometer. The NSCAT to be flown on N-ROSS is described.

Description: The following topics are addressed: (1) motivation for the National Meteorological Center (NMC) simulation project; (2) history of the NMC simulation project; (3) experimental design of the WINDSAT observing system simulation experiment; (4) preparation of the simulated observations; and (5) strengths and weaknesses of the experimental design.

Description: High-resolution cloud motion wind (CMW) data sets obtained from geostationary satellites for approximately the past decade have been used for the purpose of estimating mesoscale wind fields in various research studies. Yet there remains much controversy surrounding the proper interpretation and use of the resultant wind vector and kinematic fields. This paper is concerned with: (1) how representative are cloud draft winds of actual ambient air motions; and (2) what is the degree of practical usefulness of CMW fields for both mesoscale analysis and as input to numerical weather prediction models.

Description: A potential improvement on measuring atmospheric winds by using a coherent Doppler system has led to a need for detailed knowledge concerning the aerosol backscattering characteristics, especially at CO2 wavelengths. In order to meet this requirement, a plan of study has been developed to establish a global data base of atmospheric aerosol backscattering coefficients.

Description: Photographs of cloud scenes taken from the orbiting space shuttle are being used to assess the overestimation in the amount of cloud cover sensed by satellites at angles other than nadir. Also these photographs and Landsat images indicate that the frequency distributions of clear and of cloudy intervals, at least in simple tropical cloud scenes, may be approximated by common distribution functions.

Description: It has been proposed that a Doppler lidar be placed in a polar orbit and scanned to provide estimates of lower tropospheric winds twice per day and with a spatial resolution of 300 km. Initial feasibility studies conducted primarily by NOAA and NASA presented an optimistic outlook for a space based lidar. The technology appeared within reach and initial computer simulations suggested that acceptable accuracies could be obtained. Those early studies exposed, however, several potential problem areas which included: (1) the algorithms for computing the wind vectors did not perform well when there were coherent gradients in the wind fields; and (2) the lifetime and power requirements of the lidar put severe restrictions on the pulse repetition frequency (PRF). These two basic problems are currently being addressed by a Doppler lidar simulation study focussed upon three primary objectives: (1) to develop optimum scan parameters and shot patterns for a satellite-based Doppler lidar; (2) to develop robust algorithms for computing wind vectors from lidar returns; and (3) to evaluate the impact of coherent mesoscale structures (wind gradients, clouds, aerosols) on up-scale wind estimates. An overview is provided of the simulation efforts with particular emphasis upon rationale and methodology. Since this research is currently underway, any results shown are meant only as evidence of progress.

Description: The Wave Propagation Laboratory of the National Oceanic and Atmospheric Administration's (NOAA) Environmental Research Laboratories has investigated the feasibility of measuring the global wind field by using an infrared coherent laser radar under a joint program with the U.S. Air Force Space Division Defense Meteorological Satellite Program (DMSP). These studies considered both the analytical and hardware feasibility of a spaceborne global wind measuring coherent laser radar (WINDSAT). Objectives and requirements of the Air Force Defense Meteorological Satellite Program were used in the study. The vertical distributions of the horizontal wind field were required throughout the troposphere with 300 km square horizontal and 1 km vertical resolution with a measurements accuracy of 1 m/s. Complete global coverage was required. The lidar system performance should also be scalable to operational satellite conditions. The analytical studies were performed for both a 300 km altitude Space Shuttle orbit and an operational polar orbit of 800 km altitude (Huffaker, 1978; Huffaker et al., 1980). A hardware definition study was performed for a Space Shuttle demonstration test flight (Lockheed Missiles and Space Co., 1981). Studies have also been conducted to determine the feasibility of mounting a WINDSAT payload on an Advanced TIROS-N spacecraft (RCA Corporation, 1983).

Description: A study has been completed to define a Shuttle experiment that solves the most crucial scientific and engineering problems involved in building a satellite Doppler wind profiler for making global wind measurements. The study includes: (1) a laser study to determine the feasibility of using the existing NOAA Windvan laser in the Space Shuttle spacecraft; (2) a preliminary optics and telescope design; (3) an accommodations study including power, weight, thermal, and control system requirements; and (4) a flight trajectory and operations plan designed to accomplish the required scientific and engineering goals. The experiment will provide much-needed data on the global distribution of atmospheric aerosols and demonstrate the technique of making wind measurements from space, including scanning the laser beam and interpreting the data. Engineering accomplishments will include space qualification of the laser, development of signal processing and lag angle compensation hardware and software, and telescope and optics design. All of the results of this limited Spacelab experiment will be directly applicable to a complete satellite wind profiler for the Earth Observation System/Space Station or other free-flying satellite.

Description: WINDSAT is a proposed space based global wind measuring system. A Shuttleborne experiment is proposed as a proof of principle demonstration before development of a full operational system. WINDSAT goals are to measure wind speed and direction to + or - 1 m/s and 10 deg accuracy over the entire earth from 0 to 20 km altitude with 1 km altitude resolution. The wind measuring instrument is a coherent lidar incorporating a pulsed CO2 TEA laser transmitter and a continuously scanning 1.25 m diameter optical system. The wind speed is measured by heterodyne detecting the backscattered return laser radiation and measuring this frequency shift.

Description: Hitherto, long-range wind-sensing coherent (heterodyne) lidars have utilized CO2 lasers (operating at a 10-micrometer wavelength) since these were the only high-power single-mode (spatial and axial) pulsed sources available. This property ensures temporal coherence over the required spatial resolution, e.g., the pulse length. Recent developments in Nd:YAG lasers makes possible the consideration of a 1.06-micrometer source (Kane et al., 1984). The relative merit of operation at various wavelengths is a function of system parameter, backscattering cross section, signal processing, beam propagation, and practical and eye safety considerations. These factors are discussed in the context of a global wind-sensing coherent lidar.

Description: The rapid development of laser diodes offers the opportunity to design an all solid state transmitter for coherent Doppler lidar by using Nd:YAG as the gain medium. We have demonstrated that the components of such a system operate as expected. We believe that LD-pumped solid state laser oscillators and amplifiers offer an approach to space qualified transmitters with coherence, power, efficiency, and operating lifetime necessary to meet satellite platform requirements.

Description: Coherent laser radar systems at 10 micrometers have been studied in Europe for well over a decade. In the past few years, the level of activity has increased rapidly and work is now in progress on systems and components at a large number of research institutions and industrial firms. Some of the organizations have had specific involvement with wind and aerosol measuring lidars, while others are largely concerned with components. Some of the particular European strong points are reviewed in device physics and technology. In addition to wind measurement systems, much work has been done on other applications of coherent laser radar including ranging, imaging, and coherent DIAL studies. Some of these other applications are also outlined.

Description: Now, there are four Doppler lidar configurations which are being promoted for the measurement of tropospheric winds: (1) the coherent CO2 Lidar, operating in the 9 micrometer region using a pulsed, atmospheric pressure CO2 gas discharge laser transmitter, and heterodyne detection; (2) the coherent Neodymium doped YAG or Glass Lidar, operating at 1.06 micrometers, using flashlamp or diode laser optical pumping of the solid state laser medium, and heterodyne detection; (3) the Neodymium doped YAG/Glass Lidar, operating at the doubled frequency (at 530 nm wavelength), again using flashlamp or diode laser pumping of the laser transmitter, and using a high resolution tandem Fabry-Perot filter and direct detection; and (4) the Raman shifted Xenon Chloride Lidar, operating at 350 nm wavelength, using a pulsed, atmospheric pressure XeCl gas discharge laser transmitter at 308 nm, Raman shifted in a high pressure hydrogen cell to 350 nm in order to avoid strong stratospheric ozone absorption, also using a high resolution tandem Fabry-Perot filter and direct detection. Comparisons of these four systems can include many factors and tradeoffs. The major portion of this comparison is devoted to efficiency. Efficiency comparisons are made by estimating the number of transmitted photons required for a single pulse wind velocity estimate of + or - 1 m/s accuracy in the middle troposphere, from an altitude of 800 km, which is assured to be reasonable for a polar orbiting platform.

Description: To gain a proper perspective of the potential of coherent Doppler lidars for global wind sensing sometime in the future, we need to examine where we are, how we got here, and the expectations for future lidar system development. First we give a brief review of lidar developments leading to our present technology. Next we survey present U.S. infrared systems with particular attention to the pulsed systems since they are the ones that will have sufficient range to operate from satellites. Finally we comment on trends and probable future developments. Only unclassified lidars are considered. The considerable DoD support for classified applications certainly enhances future developments in components and subsystems.

Description: This paper describes the current status of a prototype 0.53 micrometer Doppler lidar system under development at RCA. This system consists of a frequency doubled Nd:YAG laser constrained to yield a narrow bandwidth, single frequency pulse, a Fabry-Perot Inteferometer (FPI) using an Image Plane Detector (IPD) to measure the backscatter spectrum for each pulse and a Data Acquisition System (DAS) to sample, store, and analyze the backscattered signal. These individual subsystem components have been assembled and preliminary atmospheric testing has recently begun. Atmospheric backscatter spectra are presented which demonstrate the capabilities of this system to distinguish between return signals from aerosols, molecules, and clouds.

Description: The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.

Description: Nature has provided us with a natural and easily visible method of tracing atmospheric motion through the measurement of cloud velocities. This source of wind information has been available from geosynchronous satellites since the launch of the ATS-1 Spin Scan camera. This sensor provided adequate spatial and temporal resolution views of individual cloud systems that could represent the wind with useful accuracy. During the last decade, cloud motion derived winds have become part of the operational system as they are routinely provided to the National Meteorological Center as input to the global numerical models. The principal limitations of cloud motion winds are that they (1) can be measured within the limits that cloud motions can represent the wind only where trackable clouds exist, (2) require knowledge of the cloud height, (3) require high spatial and temporal resolution geosynchronous satellite systems with high attitude determination accuracy, and (4) need sophisticated interactive computer systems for the calculation of high resolution fields. These limitations are examined and suggestions are made for how this product could be improved. Also, uses of the data for mesoscale purposes are discussed.

Description: The story of the Aircraft to Satellite Data Relay (ASDAR) program began when airline meteorologists realized that B-747's and other commercial jets provided cockpit displays of digital values for outside air temperature and winds. Later, when a few B-747's were used to carry portable air quality monitoring equipment for the Global Air Sampling Program (GASP), scientists at NASA-Lewis explored ways in which these digital values could be used to label data collected during the GASP flights. Digital values of GASP analyses were recorded along with digital values of location and altitude, time, winds, and temperature, obtained by microprocessors from within the host aircraft's avionics. These data suggested a way in which manually recorded in-flight meteorological reports could be replaced by an automatic system, which could record winds and air temperatures as often as desired. NASA's prototype ASDAR showed that automated data relay by meteorological geostationary satellites could be accomplished from an aircraft. Testing of the instruments and analyses of its data are examined.

Description: A balloon-borne triple-etalon Fabry-Perot Interferometer, observing the Doppler shifts of absorption lines caused by molecular oxygen and water vapor in the far red/near infrared spectrum of backscattered sunlight, has been used to evaluate a passive spaceborne remote sensing technique for measuring winds in the troposphere and stratosphere. There have been two successful high altitude balloon flights of the prototype UCL instrument from the National Scientific Balloon Facility at Palestine, TE (May 80, Oct. 83). The results from these flights have demonstrated that an interferometer with adequate resolution, stability and sensitivity can be built. The wind data are of comparable quality to those obtained from operational techniques (balloon and rocket sonde, cloud-top drift analysis, and from the gradient wind analysis of satellite radiance measurements). However, the interferometric data can provide a regular global grid, over a height range from 5 to 50 km in regions of clear air. Between the middle troposphere (5 km) and the upper stratosphere (40 to 50 km), an optimized instrument can make wind measurements over the daylit hemisphere with an accuracy of about 3 to 5 m/sec (2 sigma). It is possible to obtain full height profiles between altitudes of 5 and 50 km, with 4 km height resolution, and a spatial resolution of about 200 km, along the orbit track. Below an altitude of about 10 km, Fraunhofer lines of solar origin are possible targets of the Doppler wind analysis. Above an altitude of 50 km, the weakness of the backscattered solar spectrum (decreasing air density) is coupled with the low absorption crosssection of all atmospheric species in the spectral region up to 800 nm (where imaging photon detectors can be used), causing the along-the-track resolution (or error) to increase beyond values useful for operational purposes. Within the region of optimum performance (5 to 50 km), however, the technique is a valuable potential complement to existing wind measuring systems and can provide a low cost addition to powerful active (LIDAR) wind measuring systems now under development.

Description: A survey is presented of instrumentation suitable for measurement of wind near the surface of the earth by using in-situ techniques and further restricted to sensors that are operational. In this case, a sensor is deemed to be operational if it is commercially available. There is no discussion here of the systems that might be used to acquire, process, display, and store the sensor data. It is assumed that some sort of automatic data logging equipment would be used. Without special requirements such as need for high frequency response, low power consumption, etc., this treatment must be quite general and provides little detail. Also, without special restrictions, emphasis must be placed on conventional sensors that provide the bulk of wind data today.

Description: The superpressure balloon was developed to provide a method of obtaining global winds at all altitudes from 5 to 30 km. If a balloon could be made to fly for several weeks at a constant altitude, and if it could be tracked accurately on its global circuits, the balloon would provide a tag for the air parcel in which it was embedded. The Lagrangian data on the atmospheric circulation would provide a superior data input to the numerical model. The Global Atmospheric Research Program (GARP) was initiated in large part based on the promise of this technique coupled with free-floating ocean buoys and satellite radiometers. The initial name proposed by Charney for GARP was SABABURA 'SAtellite BAlloon BUoy RAdiometric system' (Charney, 1966). However, although the superpressure balloon exceeded its designers' expectations for flight duration in the stratosphere (longest flight duration of 744 days), flight duration below 10 km was limited by icing in super-cooled clouds to a few days. The balloon was relegated to a secondary role during the GARP Special Observing Periods. The several major superpressure balloon programs for global wind measurement are described as well as those new developments which make the balloon once again an attractive vehicle for measurement of global winds as a reference and bench-mark system for future satellite systems.

Description: The accuracy is studied of temperature estimates derived from the divergence equation when wind observations of various spatial and temporal resolutions and accuracies are available. The basic data set used is the high resolution model data set used by Kuo and Anthes (1984a) in observing systems simulation experiments (OSSE) designed to estimate the errors in heat and moisture budgets (Kuo and Anthes, 1984b) calculated from the AVE-SESAME-1979 spatial observational network. This model data set is modified in ways to simulate wind observations that appear feasible from an operational regional network of wind profilers.

Description: Continuous, automated measurement of tropospheric wind profiles with UHF and VHF Doppler radars has been demonstrated. Ground-based networks of these radars will be available as part of a global wind measurement system, and remote single stations could be built to further complement a spaceborne measurement device. A number of ground-based wind profilers will be in place by the time a space system is tested so the global wind measurement system should be designed with these ground-based profilers providing part of the picture.

Description: The Upper Atmosphere Research Satellite (UARS), to be launched in 1989, is to provide a global data set required to understand the mechanisms controlling upper atmosphere structure and processes, as well as the response of the upper atmosphere to natural and human perturbations. The High Resolution Doppler Imager (HRDI) is the primary instrument for measuring the dynamics of the stratosphere and mesosphere. The goal of HRDI is to measure wind velocities in the stratosphere and mesosphere during the day and the mesosphere and thermosphere at night with an accuracy of 5 m/sec. HRDI will determine winds by measuring Doppler shifts of atmosphere absorption and emission features. Line of sight winds will be taken in two directions, thus allowing the wind vector to be formed. The HRDI instrument is overviewed. The basis of the measurement is explained, as is an outline of the instrument. Since neither instrument nor observational techniques is fully mature, only a brief sketch is presented.

Description: It has been recognized for some time that water vapor structure visible in infrared imagery offers a potential for obtaining motion vectors when several images are considered in sequence (Fischer et al., 1981). A study evaluating water vapor winds obtained from the VISSR atmospheric sounder (Stewart et al., 1985) has confirmed the viability of the approach. More recently, 20 data sets have been produced from METEOSAT water vapor imagery for the FGGE period of 10-25 November 1979. Where possible, two data sets were prepared for each day at 0000 and 1200 GMT and compared with rawinsondes over Europe, Africa, and aircraft observations over the oceans. Procedures for obtaining winds were, in general, similar to the earlier study. Motions were detected both by a single pixel tracking and a cross correlation method by using three images individually separated by one hour. A height assignment was determined by matching the measured brightness temperature to the temperature structure represented by the FGGE-IIIB analyses. Results show that the METEOSAT water vapor winds provide uniform horizontal coverage of mid-level flow over the globe with good accuracy.

Description: The European Centre for Medium Range Weather Forecasts (ECMWF) is producing operational global analyses every 6 hours and operational global forecasts every day from the 12Z analysis. How the wind data are used in the ECMWF golbal analysis is described. For each current wind observing system, its ability to provide initial conditions for the forecast model is discussed as well as its weaknesses. An assessment of the impact of each individual system on the quality of the analysis and the forecast is given each time it is possible. Sometimes the deficiencies which are pointed out are related not only to the observing system itself but also to the optimum interpolation (OI) analysis scheme; then some improvements are generally possible through ad hoc modifications of the analysis scheme and especially tunings of the structure functions. Examples are given. The future observing network over the North Atlantic is examined. Several countries, coordinated by WMO, are working to set up an 'Operational WWW System Evaluation' (OWSE), in order to evaluate the operational aspects of the deployment of new systems (ASDAR, ASAP). Most of the new systems are expected to be deployed before January 1987, and in order to make the best use of the available resources during the deployment phase, some network studies are carried out at the present time, by using simulated data for ASDAR and ASAP systems. They are summarized.

Description: Two fraternal twin experiments were conducted as part of this study. A data impact experiment using real data (runs 1 and 2) was conducted to assess the impact that rawin wind observations have on both a 5-day assimilation and a single 5-day forecast generated at the end of each assimilation. An observing system simulation experiment (OSSE) using simulated observations (runs 3, 4, and 5) was conducted in order to first calibrate the OSSE results and second to use this calibration to estimate the 'real world' impact from the contribution of global 3-dimensional wind profiles generated from a space-based lidar system known as Windsat. Each of the three runs in the seond experiment were also 5-day assimilation runs with a 5-day forecast initialized from the last 6-hour update cycle of the assimilation. The data impact study revealed a consistent positive impact when rawin winds were added back into an otherwise complete FGGE data set. Both the 6-hour and 5-day forecasts were improved at all levels, in both hemispheres, and for both the wind and the geopotential height fields. Similar results were obtained from the two parallel simulation runs, 3 and 4. Together with the results from runs 1 and 2, calibration coefficients were generated so as to 'correct' the results determined from the addition of Windsat winds (run 5). The Windsat simulation showed a positive improvement in all cases studied. Even though only the tropics were enhanced with these wind observations, hemispheric rms errors were decreased in both the assimilation and 5-day forecast. The 6-hour forecasts of zonal wind from the assimilation run were improved by as much as 50 pct. on the average, and the single forecast showed an average improvement of near 30 pct. Even though these calibrated values are considered too optimistic, the skill of the forecast generated from this run extended the useful forecast period by 18-24 hours.

Description: A series of realistic simulation studies is being conducted as a cooperative effort between the European Centre for Medium Range Weather Forecasts (ECMWF), the National Meteorological Center (NMC), and the Goddard Laboratory for Atmospheres (GLA), to provide a quantitative assessment of the potential impact of future observing systems on large scale numerical weather prediction. A special objective is to avoid the unrealistic character of earlier simulation studies. Following a brief review of previous simulation studies and real data impact tests, the methodology for the current simulation system will be described. Results from an assessment of the realism of the simulation system and of the potential impact of advanced observing systems on numerical weather prediction and preliminary results utilizing this system will be presented at the conference.

Description: A brief review is presented of recent uses of ground-based wind profile data in mesoscale forecasting. Some of the applications are in real time, and some are after the fact. Not all of the work mentioned here has been published yet, but references are given wherever possible. As Gage and Balsley (1978) point out, sensitive Doppler radars have been used to examine tropospheric wind profiles since the 1970's. It was not until the early 1980's, however, that the potential contribution of these instruments to operational forecasting and numerical weather prediction became apparent. Profiler winds and radiosonde winds compare favorably, usually within a few m/s in speed and 10 degrees in direction (see Hogg et al., 1983), but the obvious advantage of the profiler is its frequent (hourly or more often) sampling of the same volume. The rawinsonde balloon is launched only twice a day and drifts with the wind. In this paper, I will: (1) mention two operational uses of data from a wind profiling system developed jointly by the Wave Propagation and Aeronomy Laboratories of NOAA; (2) describe a number of displays of these same data on a workstation for mesoscale forecasting developed by the Program for Regional Observing and Forecasting Services (PROFS); and (3) explain some interesting diagnostic calculations performed by meteorologists of the Wave Propagation Laboratory.

Description: Observational requirements are provided for the 'regional scale' (10(exp 2) to 10(exp 3) km space scale; 3 to 24 h time scale). Given this range, the regional scale represents a spatial and temporal domain in which important scale-interactive processes occur that act to concentrate large vertical wind shears, significant horizontal thermal gradients, and vertical motion patterns into narrow regions. A short review of the mass and momentum adjustments associated with jet streak-induced circulations is discussed. Evidence for the need to specify the wind field in the upper troposphere to accurately simulate forcing for the transverse circulations is also presented. The importance of specifying temperature tendency to resolve the lower tropospheric portion of the transverse circulations is highlighted. The observational requirements are then discussed, along with possible approaches for meeting the requirements on the regional scale.

Description: A passive infrared sensor is described for remote sounding of the wind field in the stratosphere and mesosphere from near Earth orbital spacecraft. The instrument uses gas correlation spectroscopy together with electro-optic phase modulation techniques to measure winds in the 20- to 120-km altitude range globally, both in the day and at night, and with a vertical resolution of better than the atmospheric scale height. Measurement of temperature and the amounts of key atmospheric species may also be made simultaneously and in coincident fields of view with the wind observations. The sensor is currently being developed at the Jet Propulsion Laboratory as a candidate for the upcoming NASA Earth Observation System.

Description: This paper reviews the current status of lidar image correlation techniques of remote wind measurement. It also examines the potential use of satellite borne lidar global wind measurements using this approach. Lidar systems can easily detect spatial variations in the volume scattering cross section of naturally occurring aerosols. Lidar derived RHI, PPI and range-time displays of aerosol backscatter have been extensively employed in the study of atmospheric structure. Descriptions of this type of data can be obtained in many references including Kunkel et al. (1977), Kunkel et al. (1980), Boers et al. (1984), Uthe et al. (1980), Melfi et al. (1985) and Browell et al. (1983). It is likely that the first space-borne lidars for atmospheric studies will observe aerosol backscatter to measure parameters such as boundary layer depth and cloud height. This paper examines the potential application of these relatively simple aerosol backscatter lidars to global wind measurements.

Description: A stated objective for this symposium is to identify requirements for global wind measurements. This paper will draw from recent reports which considered the impact of over 100 environmental factors known to affect military operations. A conclusion that can be drawn from those analyses is that one environmental factor, atmospheric wind, has an operational impact on each of the 48 mission areas examined. This paper will characterize the impact of wind on the various mission areas and will define and summarize both 'technical' and 'operational' requirements for wind intelligence.

Description: There are two theoretical arguments that have been used to discuss the relative importance of mass and wind data in numerical weather prediction (NWP). We will analyze these arguments in this section as clearly as possible in order to draw conclusions which may help to interpret experimental results on four-dimensional data assimilation, simulations of future observing systems, as well as give guidance on how to improve the efficiency with which we use the present observing system.

Description: Wind tunnel model tests of rotating cylinder wing flaps and other high lift devices for STOL AIRCRAFT

Description: Linear aerodynamic load distributions on missile and launch vehicle configurations

Description: Wind tunnel testing of dorsal-fin, delta-wing and dart-wing configurations

Description: Unsteady aerodynamics studied in Saturn launch vehicle development program

Description: Turbulent fluctuation measurements with crossed beam method

Description: High speed wind tunnel study of separation phenomenon and deterioration in aerodynamic performance from unwanted flow detachments

Description: Simulators to facilitate experimental studies of two-dimensional interaction of jet with supersonic free stream

Description: Acoustic and heat transfer aspects of launch vehicle turbulence

Description: Bursting of conical vortex sheet above delta wing surface at low speeds

Description: Steady drag and unsteady lift forces on circular cylinder subjected to two-dimensional wind flow

Description: Tilt-wing V/STOL aircraft wing stall during low powered descent

Description: Dynamic responses and motion stability for hinged helicopter rotor blade at high tip speed ratios

Description: Future research areas for NASA in private airplanes, subsonic jet transport, and hypersonic flight - general discussion

Description: Aerodynamic research program on space and launch vehicle development

Description: Flow of air around delta and other swept-back wings - vortices from apex and sheets

Description: Compressor and gas turbine engine matching - power turbine, turbojet, and turboprop engines

Description: High pressure-ratio multistage axial flow compressor operation efficiency with one or more blade rows stalled - performance prediction

Description: Charts for solution of radial distribution flow equations used in axial flow compressor design

Description: General flow equations and methods used in determining radial distributions of flow in meridional plane of axial flow compressor

Description: Potential flow theory for two-dimensional cascades, and application to fluid flow through axial flow compressors

Description: Viscous effects on two-dimensional incompressible flow about compressor blade profiles in cascade

Description: Thermodynamic equations, solution, and experimental data for aerodynamic design of axial flow compressors

Description: Three-dimensional compressor flow theory and real flow effect

Description: Steady state characteristics, stalling, and surge in axial flow compressors

Description: Design and measurement error effects on compressor performance

Description: Compressor off-design performance prediction techniques

Description: Compressor data on blade-element basis for comparison with two-dimensional cascade flow data

Description: Cycle analysis of turbojet and turboprop engines - axial flow compressor requirements for gas turbine engines

Description: Aerodynamic design of axial flow compressors

Description: Secondary and three-dimensional boundary layer flows in compressor blade rows

Description: Multistage axial flow compressor stalling characteristics and blade vibration

Description: Newtonian impact flow mathematics - application to elliptic cone, conoid of biparabolic cross sections, and drop-like blunt body

Description: Quasi-slender body theory for oscillating low aspect ratio wings and bodies of revolution in supersonic flow

Description: Impulsively started steady flow and uniformly accelerated unsteady flow about circular cylinders and mathematical models

Description: Wind and water tunnel apparatus and techniques for free stream turbulent effects on time-dependent forces acting on circular cylinders

Description: Amplitude and surface pressure measurements for circular cylinder in vortex flow-excited oscillation

Description: Wind tunnel boundary interference effects on V/STOL model aircraft test data

Description: An objective parameterization technique is developed for general nonlinear hydrodynamical systems. The typical structure of hydrodynamical systems, regardless of their complexity, is one in which the rates of change of the dependent variables depend on homogeneous quadratic and linear forms, as well as on inhomogeneous forcing terms. As a prototype of the generic problem containing this typical structure, the parameterization technique is applied to various three component subsets of a five component nonlinear spectral model of forced, dissipative quasi-geostrophic flow in a channel. The results obtained lead to specification of the necessary data coverage requirements for applying the technique in general.

Description: A steady, axisymmetric model of the general circulation is developed as a basis for climate stability studies. The model includes the effects of heating, rotation, and internal friction, but neglects topography. It is assumed that the axisymmetric flow may be modeled by making the Boussinesq and deep convection approximations. The hydrostatic assumption is not made, thus permitting the advective terms to be included in the vertical equation of motion. The initial set of five primitive equations is reduced to three equations in terms of the zonal velocity, meridional streamfunction, and the potential temperature perturbation. The application of the Boussinesq, deep convection, and quasi-geostrophic assumptions limits the ranges of the heating and rotation rates. For values not too far from typical atmospheric values, the model produces a stability boundary separating Hadley from Rossby flow. The boundary is characterized by a particular value of vertical wind shear, which suggests that baroclinic instability is the primary mechanism for the loss of stability. The initial growth rates are largest for longitudinal waves 4-7, also in agreement with studies of baroclinic instability.

Description: A two layer spectral quasi-geostrophic model is used to simulate the effects of topography on the equilibria, their stability, and the long term evolution of incipient unstable waves. The flow is forced by latitudinally dependent radiative heating. Dissipation is in the form of Rayleigh friction. An analytical solution is found for the propagating finite amplitude waves which result from baroclinic instability of the zonal winds when topography is absent. The appearance of this solution for wavelengths just longer than the Rossby radius of deformation and disappearance of ultra-long wavelengths is interpreted in terms of the Hopf bifurcation theory. Simple dynamic and thermodynamic criteria for the existence of periodic Rossby solutions are presented. A Floquet stability analysis shows that the waves are neutral. The nature of the form drag instability of high index equilibria is investigated. The proximity of the equilibrium shear to a resonant value is essential for the instability, provided the equilibrium occurs at a slightly stronger shear than resonance.

Description: Estimates of cloud street geometry produced by a model of the parallel/thermal instability modes of shallow convection are compared with observations obtained during the 1981 KonTur experiment. Good agreement between the modeled and observed orientation angles, wavelengths and Reynolds numbers are found when the streets are assumed to derive their energy from the average shear and the lowest order sine terms of a Fourier expansion of the mean wind profile (or equivalently from the lowest order cosine terms of the mean shear profile). The modes associated with the cosine terms of the wind profile (or the sine terms of the wind shear profile) do not agree well with the observations. These results suggest that the boundary layer rolls observed during KonTur might have developed owing to a combined parallel/thermal instability originating primarily from the cosine terms of the ambient roll parallel wind shear.

Description: A KC-135A aircraft equipped with wing tip winglets was flight tested to demonstrate and validate the potential performance gain of the winglet concept as predicted from analytical and wind tunnel data. Flight data were obtained at cruise conditions for Mach numbers of 0.70, 0.75, and 0.80 at a nominal altitude of 36,000 ft. and winglet configurations of 15 deg cant/-4 deg incidence, 0 deg cant/-4 deg incidence, and baseline. For the Mach numbers tested the data show that the addition of winglets did not affect the lifting characteristics of the wing. However, both winglet configurations showed a drag reduction over the baseline configuration, with the best winglet configuration being the 15 deg cant/-4 deg incidence configuration. This drag reduction due to winglets also increased with increasing lift coefficient. It was also shown that a small difference exists between the 15 deg cant/-4 deg incidence flight and wind tunnel predicted data. This difference was attributed to the pillowing of the winglet skins in flight which would decrease the winglet performance.

Description: A joint NASA/USAF program was conducted to accomplish the following objectives: (1) evaluate the benefits that could be achieved from the application of winglets to KC-135 aircraft; and (2) determine the ability of wind tunnel tests and analytical analysis to predict winglet characteristics. The program included wind-tunnel development of a test winglet configuration; analytical predictions of the changes to the aircraft resulting from the application of the test winglet; and finally, flight tests of the developed configuration. Pressure distribution, loads, stability and control, buffet, fuel mileage, and flutter data were obtained to fulfill the objectives of the program.

Description: A full-scale winglet flight test on a KC-135 airplane with an upper winglet was conducted. Data were taken at Mach numbers from 0.70 to 0.82 at altitudes from 34,000 feet to 39,000 feet at stabilized flight conditions for wing/winglet configurations of basic wing tip, 15/-4 deg, 15/-2 deg, and 0/-4 deg winglet cant/incidence. An analysis of selected pressure distribution and data showed that with the basic wing tip, the flight and wind tunnel wing pressure distribution data showed good agreement. With winglets installed, the effects on the wing pressure distribution were mainly near the tip. Also, the flight and wind tunnel winglet pressure distributions had some significant differences primarily due to the oilcanning in flight. However, in general, the agreement was good. For the winglet cant and incidence configuration presented, the incidence had the largest effect on the winglet pressure distributions. The incremental flight wing deflection data showed that the semispan wind tunnel model did a reasonable job of simulating the aeroelastic effects at the wing tip. The flight loads data showed good agreement with predictions at the design point and also substantiated the predicted structural penalty (load increase) of the 15 deg cant/-2 deg incidence winglet configuration.

Description: A joint NASA/U.S. industry program to test advanced technology airfoils in the Langley 0.3-meter Transonic Tunnel (TCT) was formulated under the Langley ACEE Project Office. The objectives include providing U.S. industry an opportunity to compare their most advanced airfoils to the latest NASA designs by means of high Reynolds number tests in the same facility. At the same time, industry would again experience in the design and construction of cryogenic test techniques. The status and details of the test program are presented. Typical aerodynamic results obtained, to date, are presented at chord Reynolds number up to 45 x 10(6) and are compared to results from other facilities and theory. Details of a joint agreement between NASA and the Deutsche Forschungs- und Versuchsantalt fur Luft- and Raumfahrt e.V. (DFVLR) for tests of two airfoils are also included. Results of these tests will be made available as soon as practical.

Description: The joint airport weather studies (JAWS) project is discussed. The major objectives of the JAWS Project are a fundamental description of the phenomenon, a determination of the hazard potential and a definition of a protection and warning system, all of which are relative to low level wind shear. Aspects of the low level wind shear phenomenon. The principal focus, however, is the microburst. The microburst is fundamentally a rather simple atmospheric flow. It is a downdraft that, upon approaching the surface, spreads out horizontally, producing a diverging radial flow in all directions. For any direction that an aircraft flies through the microburst, it will first encounter increasing head winds; then the remnants of the downdraft; and then, increasing tail wind.

Description: A heavily instrumented F-106B aircraft was flown in thunderstorms to gather data for characterizing lightning at aircraft operating altitudes. Conventional weather finding techniques are supplemented with UHF lightning mapping radar to select the most active storm cells and the most likely altitude for obtaining direct lightning strikes to the airplane. One hundred seventy-six strikes were obtained in a 3 year period, mostly at an altitude of above 25,000 feet.

Description: A wind shear and vortex wake and their impact on aircraft were investigated. The systems and advice to help pilots, and rational scientific methods to assist in advising certification authorities and those interested in improving flight safety were developed. Wind Shear and Vortex Wakes are related, they are both invisible enemies of aircraft in the form of large disturbances in the atmosphere, both cause major accidents. Problems of building wakes at airports are is considered. Research on wind shear was initiated by the American FAA following the Boston, New York and Denver accidents to civil airliners. This resulted in: useful advice to pilots about wind shear; better attempts by the meteorologists at forecasting wind shear conditions; and useful ideas for wind shear measurement and warning systems. Three major research tasks are outstanding: (1) Worldwide measurements to give reliable estimates of probability and details of the forms of large wind shears; (2) Developments of real time wind shear measuring systems for ground or airborne use; and (3) Establishing relationships between measured wind shear and the potential hazard to an aircraft, or class of aircraft.

Description: Marked surface inversions occur most frequently in dry continental climates, where low atmospheric humidity allows heat transfer by long wave thermal radiation. In the northern latitudes, surface inversions reach their maximum intensity during the winter, when the incoming Sun's radiation is negligible and radiative cooling is dominant during the long nights. During winter, air mass boundaries are sharp, which causes formation of marked surface inversions. The existence of these inversions and sharp boundaries increase the risk of wind shear. The information should refer to marked inversions exceeding a temperature difference of 10 deg C up to 1000 feet. The need to determine the temperature range over which he information is operationally needed and the magnitude of the inversion required before a notification to pilots prior to departure is warranted are outlined.

Description: The Gust Gradient Program is a data intensive effort involving tripple Doppler radar, a surface weather station mesonet and other aircraft. The Joint Airport Weather Studies was utilized to gain additional data. The data were used to fill in the gap in turbulence modeling.

Description: The objective of the Generalized Exponential Markov (GEM) Program was to develop a weather forecast guidance system that would: predict between 0 to 6 hours all elements in the airways observations; respond instantly to the latest observed conditions of the surface weather; process these observations at local sites on minicomputing equipment; exceed the accuracy of current persistence predictions at the shortest prediction of one hour and beyond; exceed the accuracy of current forecast model output statistics inside eight hours; and be capable of making predictions at one location for all locations where weather information is available.

Description: Recommendations based on need, cost, and achievement of flight safety are offered, and the re-evaluation of weather parameters needed for safe landing operations that lead to reliable and consistent automated observation capabilities are considered.

Description: The primary responsibilities of the National Weather Service (NWS) are to: provide warnings of severe weather and flooding for the protection of life and property; provide public forecasts for land and adjacent ocean areas for planning and operation; and provide weather support for: production of food and fiber; management of water resources; production, distribution and use of energy; and efficient and safe air operations.

Description: The implementation of the National Airspace System (NAS) will improve safety services to aviation. These services include collision avoidance, improved landing systems and better weather data acquisition and dissemination. The program to improve the quality of weather information includes the following: Radar Remote Weather Display System; Flight Service Automation System; Automatic Weather Observation System; Center Weather Processor, and Next Generation Weather Radar Development.

Description: Rainfall characteristics using data from dense recording raingage networks is reviewed. Data from such networks have quantified temporal and spatial rainfall distributions, and have supplied specialized information about local and orographic effects. The natural variability, temporally and spatially, for annual, seasonal, monthly, and individual events is treated. Especially important are the spatial variations of precipitation as a function of synoptic type, precipitation type, amount, and duration. Results from dense raingage networks in Illinois, and some data from other climatic regions is also treated.

Description: A 10 channel scanning radiometer, built as a prototype for the coastal zone color scanner on the Nimbus 7 satellite, was flown on a high altitude aircraft during a Gymnodium breve bloom along the west coast of Florida. The remotely measured ocean color imagery shows what is probably the patchy structure of a G. breve bloom extending over a 60 km by 100 km area. This conclusion is based on visual inspection of bathymetry to infer bottom reflection trends and on a single growth truth measurement of B G. breve obtained the previous day. The image shows coherent blooms which extend scales up to 60 km in length.

Description: The snowmelt-runoff model developed for two small central European watersheds simulate daily streamflow on the 228 sq km Dinwoody Creek basin in Wyoming, using snowcover extent for LANDSAT and conventionally measured temperature and precipitation. For the six-month snowmelt seasons of 1976 and 1974, the simulated seasonal runoff volumes were within 5 and 1%, respectively, of the measured runoff. Also the daily fluctuations of discharge were simulated to a high degree by the model. Thus far the limiting basin size for applying the model has not been reached, and improvements can be expected if the hydrometeorological data can be obtained from a station inside the basin. LANDSAT provides an efficient way to obtain the critical snowcover input parameter required by the model.

Description: A large scale numerical time-dependent model of sea ice that takes into account the heat fluxes in and out of the ice, the seasonal occurrence of snow, and ice motions was used in an experiment to determine the response of the Arctic Ocean ice pack to a warming of the atmosphere. The degree of warming specified is that expected for a doubling of atmospheric carbon dioxide with its associated greenhouse effect, a condition that could occur before the middle of the next century. The results of three 5-year simulations with a warmer atmosphere and varied boundary conditions were: (1) that in the face of a 5 K surface atmospheric temperature increase the ice pack disappeared completely in August and September but reformed in the central Arctic Ocean in mid fall; (2) that the simulations were moderately dependence on assumptions concerning cloud cover; and (3) that even when atmospheric temperature increases of 6-9 K were combined with an order-of-magnitude increase in the upward heat flux from the ocean, the ice still appeared in winter. It should be noted that a year-round ice-free Arctic Ocean has apparently not existed for a million years or more.

Description: During the summer of 1977, fire totaled 44 sq km of tundra vegetation according to measurements using LANDSAT imagery. Based on the experience gained from analysis of this fire using ground observations, satellite imagery, and topographic maps, it appears that natural drainages form effective fire breaks on the subdued relief of the Arctic coastal plain and northern foothills. It is confirmed that the intensity of the fire is related to vegetation type and to the moisture content of the organic rich soils.

Description: Mass entrainment of round turbulent jet exhausting into cross flow

Description: The geostationary and polar satellites comprising the current operational system are discussed. The data acquisition capabilities of both satellite types and their complementary functions are reviewed. The advanced very high resolution radiometer on the TIROS N satellites is particularly addressed along with the imaging and atmospheric sounding instrumentation aboard the GOES satellites. The dissemination of the satellite data to the prospective users is also discussed.