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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Atmospheric temperatures near the tropical tropopause Temporal variations, zonal asymmetry and implications for stratospheric water vapor

Analysis of temperature measurements obtained over an eight-year period in the vicinity of the low-latitude tropopause confirms the existence of longitude regions which are consistently colder by approximately 2-3 K than elsewhere in the tropics. These temperature differences, however, are confined to a layer of thickness 3-5 km centered on the tropopause. The lowest monthly mean temperatures observed at the colder stations yield saturation mixing ratios that are consistent with the range of measured stratospheric water vapor. Examination of the daily variations in temperature at a given station reveals a more complex pattern than indicated by the monthly averages. On many days temperatures at the colder longitudes correspond to water vapor abundances that are less than observed in the stratosphere despite the favorable comparison of the monthly means. The results point to the need for a series of water vapor soundings at selected longitudes and times in order to define the extent to which the tropical tropopause controls the stratospheric water vapor abundance.

Frederick, J. E.↗
NASA NTRS1985

The lateral surface drag coefficient of cylindrical spacecraft in a rarefied finite temperature atmosphere

In the present determination of the free molecule flow drag coefficient for a cylindrical spacecraft flying parallel to its principal axis, the lateral surface effects of thermal motion are explicitly included in terms of the average impact angle of the incident gas momentum vector. Kinetic theory is used to characterize self-shadowing, as well as to obtain an expression for the lateral surface coefficient in terms of the average impact angle of the incident momentum vector and the fractional momentum transfer along the line of impact. It is found that, for a length/diameter ratio of about 5, the lateral surface contribution to the drag coefficient is comparable to that of the front face.

Herrero, F. A.↗
NASA NTRS1989

Tunable diode laser measurements of line widths in the nu1-fundamental band of (N-14)2(O-16) at atmospheric temperatures

A tunable diode-laser spectrometer and a low-temperature absorption cell have been employed to measure the N2-broadened and O2-broadened half-widths of rotational lines in the nu1 fundamental band of (N-14)2(O-16) at 185, 235, 263, and 295 K. The temperature dependence of the line widths has been observed to be practically identical, thereby leading to the suggestion that air-broadening would exhibit the same dependence.

Varanasi, P.↗
NASA NTRS1989

Linewidth measurements in the thermal infrared bands of (C-12)H3D at planetary atmospheric temperatures

Collision-broadened halfwidths of three lines in the nu3 fundamental band and of four lines in the nu6 fundamental band of (C-12)H3D have been measured at temperatures between 123 and 295 K using the Doppler-limited spectral resolution of a tunable diode laser spectrometer. Temperature dependence of the linewidths has been determined in self-broadening and in broadening by H2, He and N2.

Varanasi, Prasad↗
NASA NTRS1992

An evaluation of monthly mean MSU and ECMWF global atmospheric temperatures for monitoring climate

The usefulness of global satellite sounding data for monitoring climate was assessed by comparing monthly mean brightness temperature anomalies derived from channel 2 of the microwave sounding units (MSUs) on board NOAA satellites over the past decade with both weighted and pressure-level ECMWF monthly mean temperatures for 96 months from 1982 to 1989. Results show that very good agreement exists between the MSU and the weighted ECMWF temperatures over the period considered, with grid-point correlations exceeding 0.85. Comparisons with individual pressure-level temperatures from ECMWF showed high correlations at 300 mb over most of the globe.

Hurrell, James W.↗
NASA NTRS2004

Jupiter's Atmospheric Temperatures: From Voyager IRIS to Cassini CIRS

Retrievals run on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby have been used to generate global temperature maps of the planet in the troposphere and stratosphere. Similar retrievals were performed on Voyager 1 IRIS data and have provided the first detailed IRIS map of the stratosphere. In both data sets, high latitude troposphere temperatures are presented for the first time, and the meridional gradients indicate the presence of circumpolar jets. Thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes. The temperatures retrieved from the two spacecraft were also compared with yearly ground-based data obtained over the intervening two decades. Tropospheric temperatures reveal gradual changes at low latitudes, with little obvious seasonal or short-term variation (Orton et al. 1994). Stratospheric temperatures show much more complicated behavior over short timescales, consistent with quasi-quadrennial oscillations at low latitudes, as suggested in prior analyses of shorter intervals of ground- based data (Orton et al. 1991, Friedson 1999). A scaling analysis indicates that meridional motions, mechanically forced by wave or eddy convergence, play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter time scales. At latitudes away from the equator, the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative. Ground-based observations with improved vertical resolution and/or long-term monitoring from spacecraft are required for this purpose.

Simon-Miller, Amy A.↗
NASA NTRS2005

Should We Believe Atmospheric Temperatures Measured by Entry Accelerometers Traveling at "Slow" Near-Sonic Speeds?

Mars Pathfinder's Accelerometer instrument measured an unexpected and large temperature inversion between 10 and 20 kilometer altitude. Other instruments have failed to detect similar temperature inversions. I test whether this inversion is real or not by examining what changes have to be made to the assumptions in the accelerometer data processing to obtain a more "expected" temperature profile. Changes in derived temperature of up to 30K, or 15%, are necessary, which correspond to changes in derived density of up to 25% and changes in derived pressure of up to 10%. If the drag coefficient is changed to satisfy this, then instead of decreasing from 1.6 to 1.4 from 20 kilometers to 10 kilometers, the drag coefficient must increase from 1.6 to 1.8 instead. If winds are invoked, then speeds of 60 meters per second are necessary, four times greater than those predicted. Refinements to the equation of hydrostatic equilibrium modify the temperature profile by an order of magnitude less than the desired amount. Unrealistically large instrument drifts of 0.5-1.0 meters per square second are needed to adjust the temperature profile as desired. However, rotational contributions to the accelerations may have the necessary magnitude and direction to make this correction. Determining whether this hypothesis is true will require further study of the rigid body equations of motion, with detailed knowledge of the positions of all six accelerometers. The paradox concerning this inversion is not yet resolved. It is important to resolve it because the paradox has some startling implications. At one extreme, are temperature profiles derived from accelerometers inherently inaccurate by 20K or more? At the other extreme, are RS temperature profiles inaccurate by this same amount?

Withers, Paul↗
NASA NTRS2008

Improved Determination of Surface and Atmospheric Temperatures Using Only Shortwave AIRS Channels

The Goddard DAAC has been analyzing AIRS/AMSU sounding data using the AIRS Science Team Version 5 retrieval algorithm. The AIRS Version 5 retrieval algorithm produces significantly better temperature profiles under more difficult cloud conditions than does the AIRS Version 4 algorithm, because, following theoretical considerations, it employs 15 micron CO2 tropospheric sounding channels only for the purpose of generating cloud cleared radiances for all AIRS channels, and determines temperature profiles using only 4.2 micron AIRS observations. This approach works equally well during both daytime and night time conditions. The AIRS Version 6 retrieval algorithm takes this approach one step further, and now also determines surface skin temperatures over both land and ocean, using only shortwave AIRS window channel cloud cleared radiances. Shortwave surface spectral emissivity and spectral bi-directional reflectance are solved for simultaneously along with the surface skin temperature. Longwave surface spectral emissivity is determined in a subsequent step using only AIRS longwave window channels, using the previously determined surface skin temperature. The methodology to do this will be described, and results will be presented demonstrating significant improvement in retrieved surface skin temperatures and surface spectral emissivities compared to those obtained using Version 5, both day and night.

Susskind, Joel↗
NASA NTRS2013

A 6U CubeSat Constellation for Atmospheric Temperature and Humidity Sounding

We are currently developing a 118/183 GHz sensor that will enable observations of temperature and precipitation profiles over land and ocean. The 118/183 GHz system is well suited for a CubeSat deployment as ~10cm antenna aperture provides sufficiently small footprint sizes (is approx. 25km). This project will enable low cost, compact radiometer instrumentation at 118 and 183 GHz that would fit in a 6U CubeSat with the objective of mass-producing this design to enable a suite of small satellites to image the key geophysical parameters that are needed to improve prediction of extreme weather events. We will take advantage of past and current technology developments at JPL viz. HAMSR (High Altitude Microwave Scanning Radiometer), Advanced Component Technology (ACT'08) to enable low-mass and low-power high frequency airborne radiometers. The 35 nm InP enabling technology provides significant reduction in power consumption (Low Noise Amplifier + Mixer Block consumes 24 mW). In this paper, we will describe the design and implementation of the 118 GHz temperature sounder and 183 GHz humidity sounder instrument on the 6U CubeSat. In addition, a summary of radiometer calibration and retrieval techniques of the temperature and humidity will be discussed. The successful demonstration of this instrument on the 6U CubeSat would pave the way for the development of a constellation consisting of suite of these instruments. The proposed constellation of these 6U CubeSat radiometers would allow sampling of tropospheric temperature and humidity with fine temporal (on the order of minutes) and spatial resolution (is approx. 25 km).

radiometer↗
NASA NTRS2006

Surface Emissivity Effects on Thermodynamic Retrieval of IR Spectral Radiance

The surface emissivity effect on the thermodynamic parameters (e.g., the surface skin temperature, atmospheric temperature, and moisture) retrieved from satellite infrared (IR) spectral radiance is studied. Simulation analysis demonstrates that surface emissivity plays an important role in retrieval of surface skin temperature and terrestrial boundary layer (TBL) moisture. NAST-I ultraspectral data collected during the CLAMS field campaign are used to retrieve thermodynamic properties of the atmosphere and surface. The retrievals are then validated by coincident in-situ measurements, such as sea surface temperature, radiosonde temperature and moisture profiles. Retrieved surface emissivity is also validated by that computed from the observed radiance and calculated emissions based on the retrievals of surface temperature and atmospheric profiles. In addition, retrieved surface skin temperature and emissivity are validated together by radiance comparison between the observation and retrieval-based calculation in the window region where atmospheric contribution is minimized. Both simulation and validation results have lead to the conclusion that variable surface emissivity in the inversion process is needed to obtain accurate retrievals from satellite IR spectral radiance measurements. Retrieval examples are presented to reveal that surface emissivity plays a significant role in retrieving accurate surface skin temperature and TBL thermodynamic parameters.

Zhou, Daniel K.↗
NASA NTRS1976

Neutral temperature of cometary atmospheres

Spectral analyses of the coma and type I tails of a comet indicate that the main constituent of a cometary atmosphere is H2O and that cometary nuclei are composed of dirty ice containing mainly CO and N2. Thermochemical calculations on strong infrared coupling between H2O and dust grains explain the dependence of atmospheric temperature on the distance of the comet from the sun considering the strong cooling effect of H2O. It is concluded that atmospheric temperatures of comets cannot be so high as 1500 K.

Shimizu, M.↗
NASA NTRSDate not supplied

Wind Lidars for Aero-Assisted Entry, Descent, and Landing on Mars

NASA seeks to safely and consistently deliver 20 metric tons of payload to within 50m of the intended location on Mars. A study has been conducted to evaluate the utility of wind lidars to aid in aero-assisted entry, descent, and precision landing of vehicles carrying these payloads. Numerical simulation found that coherent-Doppler, infrared, aerosol-backscatter wind lidars on the Martian surface can measure winds nominally over a 15km radius hemisphere using eye-safe laser energies and optical apertures similar to those commercially available for terrestrial airport support. Such ground-based wind measurements around the target delivery site are useful for determining when to initiate atmospheric entry. Initial analyses of direct-Doppler, ultraviolet, molecular-backscatter wind lidars demonstrateforward-looking measurement of wind speed, atmospheric temperature, atmospheric density, and vehicle flight attitude beyond the vehicle boundary layer. These measurements would enable controlled flight of an aero-assisted cargo vehicle to the designated landing site.

Mars↗