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NASA NTRS1983

Atmospheric soundings from a geostationary satellite

The accuracy of the soundings from a geostationary platform with the visible infrared spin-scan radiometer atmospheric sounder (VAS) on GOES-5 is evaluated. It is shown that the VAS radiances for the case under investigation are consistent with those obtained by the polar orbiting high resolution infrared radiation sounders. VAS temperature profile retrievals are found to agree well with those observed by radiosonde. An improved product can be obtained by initializing the retrieval process with ground-based Profiler data. It is found that time variations in the atmospheric state are readily discernible from VAS soundings at approximately 2 hr intervals. The results of this case study show that merging ground Profiler and satellite VAS observations can provide temperature soundings of comparable accuracy to those of the radiosonde, although the VAS-Profiler sounding can be achieved much more frequently.

Menzel, W. P.↗

NASA NTRS1984

The impact of satellite temperature soundings on the forecasts of a small national meteorological service

The impact of introducing satellite temperature sounding data on a numerical weather prediction model of a national weather service is evaluated. A dry five level, primitive equation model which covers most of the Northern Hemisphere, is used for these experiments. Series of parallel forecast runs out to 48 hours are made with three different sets of initial conditions: (1) NOSAT runs, only conventional surface and upper air observations are used; (2) SAT runs, satellite soundings are added to the conventional data over oceanic regions and North Africa; and (3) ALLSAT runs, the conventional upper air observations are replaced by satellite soundings over the entire model domain. The impact on the forecasts is evaluated by three verification methods: the RMS errors in sea level pressure forecasts, systematic errors in sea level pressure forecasts, and errors in subjective forecasts of significant weather elements for a selected portion of the model domain. For the relatively short range of the present forecasts, the major beneficial impacts on the sea level pressure forecasts are found precisely in those areas where the satellite sounding are inserted and where conventional upper air observations are sparse. The RMS and systematic errors are reduced in these regions. The subjective forecasts of significant weather elements are improved with the use of the satellite data. It is found that the ALLSAT forecasts are of a quality comparable to the SAR forecasts.

Wolfson, N.↗

NASA NTRS1984

VAS sounding data evaluation

The VAS soundings derived by NOAA personnel and NASA personnel and rawinsonde soundings are compared: (1) directly by plotting on Skew t-log p diagrams; (2) by pairing rawinsonde soundings with the closest satellite soundings and calculating the mean and standard deviations of differences between the two data sets; and (3) by constructing synoptic and subsynoptic scale analyses with rawinsonde and satellite data. Differences for various parameters are discussed.

Scoggins, J. R.↗

NASA NTRS1984

A comparison of U.S. and USSR rocketsondes using LIMS satellite temperature sounding as a transfer standard

In connection with the reduction of the number of sounding rockets launched per year, there is a general need to make the most effective use of each sounding. In particular, it is often necessary to combine the results from different types of instruments to obtain a meaningful and complete picture of the atmosphere. For this reason, data from different rockets must be compatible. The present investigation is concerned with the utilization of the temperature soundings of the Limb Infrared Monitor of the Stratosphere (LIMS) as the uniform comparison standard. Gille et al. (1984) have compared the LIMS temperatures to a set of 122 U.S. datasonde rockets. In the current study, a comparison between soundings by rocketborne instruments of the USSR and LIMS is combined with the results of the previous LIMS-U.S. rocketsonde comparison in the same latitude bands to provide an updated estimate of the differences between U.S. and USSR rocketborne temperature measurements.

Gille, J. C.↗

NASA NTRS1986

Flow field and near and far sound field of a subsonic jet

Flow and sound field data are presented for a 2.54 cm diameter air jet at a Mach number of 0.50 and a Reynolds number of 300,000. Distributions of mean velocity, turbulence intensities, Reynolds stress, spectral components of turbulence as well as of the near field pressure, together with essential characteristics of the far field sound are reported. This detailed set of data for one particular flow, erstwhile unavailable in the literature, is expected to help promoote and calibrate subsonic jet noise theories. 'Source locations' in terms of the turbulence maxima, coupling between the entrainment dynamics and the near pressure field, the sound radiation paths, and the balance in mass, momentum and sound energy fluxes are discussed. The results suggest that the large scale coherent structures of the jet govern the 'source locations' by controlling the turbulence and also strongly influence the near field pressure fluctuations.

Zaman, K. B. M. Q.↗

NASA NTRS1986

Remote temperature profiling in the troposphere and stratosphere by the radio-acoustic sounding technique

Radar application of the radio-acoustic sounding technique uses the Doppler frequency shift of radar echoes returning from the atmospheric wave structure, in association with a traveling acoustic pulse transmitted from the ground, to determine the speed of sound, and hence the atmospheric temperature, as a function of altitude. Temperature measurement in the troposphere and stratosphere were determined using the radio-acoustic sounding technique with the Radio-Acoustic Sounding System (RASS). Successful experiments were performed in March 1985, and in August 1985.

Matuura, N.↗

NASA NTRS1985

Time composite sounding

In the time composite sounding mode, the Vertical Atmospheric Sounder (VAS) data is collected in a series of images of one spin each rather than in the dwell sound mode where single lines are repeatedly scanned. A drawback of the time composite method is temporal smearing of the data, but to compensate this there is also the chance that shifting cloud patterns will permit better spatial coverage. Time composite sounding was performed for a single case study, June 14, 1984. Four, ten minute single spin swaths were processed. The principal conclusion was that the time composite results were at least equivalent to the conventional dwell sounding results, despite the fact that compositing was done in a less than optimum way because of software limitations.

Hayden, C.↗

NASA NTRS1987

X-ray astronomy experiments from sounding rockets

During the past fourteen years, the M.I.T. X-ray Astronomy sounding rocket group has designed, fabricated, and flown five different scientific sounding rocket payloads. These experiment payloads were launched on a total of twelve sounding rocket flights of which only one failed because of rocket problems. Eight of these flights yielded astronomical data that resulted in a total of twelve publications. The bulk of this research was supported by NASA Grant NGR 22-009-730 X-Ray Astronomy Experiments Sounding Rockets. The fifth and final experiment payload conceived and built under this Grant (the Wide Field Soft X-ray Camera: WFSXC) served as the prototype for the British Wide Field Camera (WFC) experiment to be launched on the ROSAT mission. The five experiment payloads and the results obtained from these experiments are briefly described. In the case of the WFSXC, which served principally as an engineering prototype for a major space mission, a number of papers written by British collaborators which describe the ROSAT Wide Field Camera are presented.

Rappaport, Saul↗

NASA NTRS1987

Sound propagation over uneven ground and irregular topography

The acoustic impedance of the surface coverings used in the laboratory experiments on sound diffraction by topographical ridges was determined. The model, which was developed, takes into account full wave effects and the possibility of surface waves and predicts the sound pressure level at the receiver location relative to what would be expected if the flat surface were not present. The sound pressure level can be regarded as a function of frequency, sound speed in air, heights of source and receiver, and horizontal distance from source to receiver, as well as the real and imaginary parts of the surface impedance.

Berthelot, Yves H.↗

NASA NTRS1987

Improved VAS regression soundings of mesoscale temperature structure observed during the 1982 atmospheric variability experiment

An Atmospheric Variability Experiment (AVE) was conducted over the central U.S. in the spring of 1982, collecting radiosonde date to verify mesoscale soundings from the VISSR Atmospheric Sounder (VAS) on the GOES satellite. Previously published VAS/AVE comparisons for the 6 March 1982 case found that the satellite retrievals scarcely detected a low level temperature inversion or a mid-tropospheric cold pool over a special mesoscale radiosonde verification network in north central Texas. The previously published regression and physical retrieval algorithms did not fully utilize VAS' sensitivity to important subsynoptic thermal features. Therefore, the 6 March 1982 case was reprocessed adding two enhancements to the VAS regression retrieval algorithm: (1) the regression matrix was determined using AVE profile data obtained in the region at asynoptic times, and (2) more optimistic signal-to-noise statistical conditioning factors were applied to the VAS temperature sounding channels. The new VAS soundings resolve more of the low level temperature inversion and mid-level cold pool. Most of the improvements stems from the utilization of asynoptic radiosonde observations at NWS sites. This case suggests that VAS regression soundings may require a ground-based asynoptic profiler network to bridge the gap between the synoptic radiosonde network and the high resolution geosynchronous satellite observations during the day.

Chesters, Dennis↗

NASA NTRS1986

Sounding rocket and balloon flight safety philosophy and methodologies

NASA's sounding rocket and balloon goal is to successfully and safely perform scientific research. This is reflected in the design, planning, and conduct of sounding rocket and balloon operations. The purpose of this paper is to acquaint the sounding rocket and balloon scientific community with flight safety philosophy and methodologies, and how range safety affects their programs. This paper presents the flight safety philosophy for protecting the public against the risk created by the conduct of sounding rocket and balloon operations. The flight safety criteria used to implement this philosophy are defined and the methodologies used to calculate mission risk are described.

Beyma, R. J.↗

NASA NTRS1987

Measurement of the absorption coefficient of acoustical materials using the sound intensity method

In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined by measuring the intensity incident on the sample and the intensity reflected by the sample placed in a reverberation chamber. Absorption coefficient results obtained by the sound intensity technique were compared with standard techniques, namely the reverberation chamber and the standing wave tube. The major advantages of using the sound intensity technique are that it permits 'in situ' measurements and the absorption coefficient for a large range of frequencies can be obtained from a single measurement.

Atwal, Mahabir S.↗

NASA NTRS1990

Analysis of diurnal variation of SCu layer using 2 days of CLASS soundings on San Nicolas Island

Sixty-nine soundings were taken at San Nicolas Island during the FIRE marine stratocumulus experiment. The archived thermodynamic data at 5mb vertical resolution were reduced to 25mb vertical resolution by averaging. Ceilometer data showed the time variation of cloud-base. A subset of 20 soundings taken during a 2 day period of light winds were analyzed. The soundings are grouped into 6 hr. averages (with 5 soundings in each category) to examine the diurnal variation of the thermodynamic structure. Consistent with the solar heating during the daytime, cloud-base rises during the daytime hours and the cloud layer thins. The subcloud layer also becomes more stable, suggesting some uncoupling of the cloud layer from the surface.

Betts, Alan K.↗

NASA NTRS1990

Third-sound propagation in thick films of superfluid He-4

Atkins' (1959) basic theory of third sound in thick films of superfluid He-4 is extended here to include a heat source for exciting third sound. A one-dimensional model obeying periodic boundary conditions is developed which can represent a variety of experimentally important configurations. General solutions for the model equations are found which give a complete description of third-sound waves in terms of displacement of the film surface, superfluid velocity, and temperature change as functions of space and time. Algebraic expressions for quantities that occur in general formulas are found for special excitation signals. The structure of third sound is calculated for the first time and the results are found to be inconsistent with previous findings. A direct method for accurately measuring the vaporization coefficient is also presented.

Jackson, H. W.↗

NASA NTRS1991

Future hybrid infrared and microwave satellite sounding system - A theoretical analysis of its capability

The expected atmospheric sounding accuracy and the vertical resolution performance of the sounding system selected by NASA to fly aboard the Earth Observing System polar platform, the Atmospheric Infrared Sounder combined with the Advanced Microwave Sounding Unit, are evaluated under various weather conditions. The performance of the combined system is compared to that of current polar orbiting systems. The complementary nature of the IR component provides high vertical resolution, and the microwave information permits sounding through nonprecipitating clouds.

Huang, H.-L.↗

NASA NTRS1993

The use of polar-orbiting satellite sounding data to estimate rural maximum and minimum temperatures

Atmospheric sounding products from NOAA's polar-orbiting satellites were used to derive and test predictive equations of rural shelter-level maximum and minimum temperatures. Sounding data from both winter and summer months were combined with surface data from over 5300 cooperative weather stations in the continental United States to develop multiple linear regression equations. Separate equations were developed for both maximum and minimum temperature, using the three types of sounding retrievals (clear, partly cloudy, and cloudy). Clear retrieval models outperformed others, and maximum temperatures were more accurately predicted than minimums. Average standard deviations of observed rural shelter temperatures within sounding search areas were of similar magnitude to root-mean-square errors from satellite estimates for most clear and partly cloudy cases, but were significantly less for cloudy retrieval cases. Model validation for surrogate polar and tropical climatic regions showed success in application of the four clear retrieval models (maximum and minimum temperature, for both winter and summer). This indicates the potential adaptability of these models to estimates of rural shelter temperature in areas outside of the United States.

Johnson, Gregory L.↗

NASA NTRS1994

Numerical model for the weakly nonlinear propagation of sound through turbulence

When finite amplitude (or intense) sound, such as a sonic boom, propagates through a turbulent atmosphere, the propagation is strongly affected by the turbulence. The interaction between sound and turbulence has mostly been studied as a linear phenomenon, i.e., the nonlinear behavior of the intense sound has been neglected. It has been shown that turbulence has an effect on the perceived loudness of sonic booms, mainly by changing its peak pressure and rise time. Peak pressure and rise time are important factors that determine the loudness of the sonic boom when heard outdoors. However, the interaction between turbulence and nonlinear effects has mostly not been included in propagation studies of sonic booms. It is therefore important to investigate the influence of acoustical nonlinearity on the interaction of intense sound with turbulence.

Lipkens, Bart↗

NASA NTRS1994

The integrated sounding system: Description and preliminary observations from TOGA COARE

An Integrated Sounding System (ISS) that combines state-of-the-art remote and in situ sensors into a single transportable facility has been developed jointly by the National Center for Atmospheric Research (NCAR) and the Aeronomy Laboratory of the National Oceanic and Atmospheric Administration (NOAA/AL). The instrumentation for each ISS includes a 915-MHz wind profiler, a Radio Acoustic Sounding System (RASS), an Omega-based NAVAID sounding system, and an enhanced surface meteorological station. The general philosophy behind the ISS is that the integration of various measurement systems overcomes each system's respective limitations while taking advantage of its positive attributes. The individual observing systems within the ISS provide high-level data products to a central workstation that manages and integrates these measurements. The ISS software package performs a wide range of functions: real-time data acquisition, database support, and graphical displays; data archival and communications; and operational and posttime analysis. The first deployment of the ISS consists of six sites in the western tropical Pacific--four land-based deployments and two ship-based deployments. The sites serve the Coupled Ocean-Atmosphere Response Experiment (COARE) of the Tropical Ocean and Global Atmosphere (TOGA) program and TOGA's enhanced atmospheric monitoring effort. Examples of ISS data taken during this deployment are shown in order to demonstrate the capabilities of this new sounding system and to demonstrate the performance of these in situ and remote sensing instruments in a moist tropical environment. In particular, a strong convective outflow with a pronounced impact of the atmospheric boundary layer and heat fluxes from the ocean surface was examined with a shipboard ISS. If these strong outflows commonly occur, they may prove to be an important component of the surface energy budget of the western tropical Pacific.

Parsons, David↗