Search NASA⌕ Search

SEARCH · Search NASA

Results for “WATER VAPOR”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Water Vapor on Titan: The Stratospheric Vertical Profile from Cassini/CIRS Infrared Spectra

Water vapor in Titan's middle atmosphere has previously been detected only by disk-average observations from the Infrared Space Observatory (Coustenis et al., 1998). We report here the successful detection of stratospheric water vapor using the Cassini Composite Infrared Spectrometer (CIRS, Flasar et al., 2004) following an earlier null result (de Kok et al., 2007a). CIRS senses water emissions in the far-infrared spectral region near 50 microns, which we have modeled using two independent radiative transfer and inversion codes (NEMESIS, Irwin et al 2008 and ART, Coustenis et al., 2010). From the analysis of nadir spectra we have derived a mixing ratio of (0.14 plus or minus 0.05) ppb at 100 km, corresponding to a column abundance of approximately (3.7 plus or minus 1.3) x 10(exp 14) moles per square centimeter. Using limb observations, we obtained mixing ratios of (0.13 plus or minus 0.04) ppb at 125 km and (0.45 plus or minus 0.15) ppb at 225 km of altitude, confirming that the water abundance has a positive vertical gradient as predicted by photochemical models. In the latitude range (80 deg. S - 30 deg. N) we see no evidence for latitudinal variations in these abundances within the error bars.

Cottini, V.↗
NASA NTRS1998

Evaluation of Terms in the Water Vapor Budget Using Airborne Dial and In Situ Measurements from the Southern Great Plans 1997 Experiment

The Southern Great Plains (SGP97) field experiment was conducted in Oklahoma during June and July 1997 primarily to validate soil moisture retrieval algorithms using microwave radiometer measurements from aircraft as well as in situ surface measurements. One important objective of the SGP97 experiment plan was to examine the effect of soil moisture on the evolution of the atmospheric boundary layer (ABL) and clouds over the Southern Great Plains during the warm season. To support boundary layer studies during SGP97. the NASA Langley Research Center's Lidar Atmospheric Sensing Experiment (LASE) was flown on a NASA-P3 aircraft in conjunction with the Electronically Scanned Thinned Array Radiometer (ESTAR). The LASE instrument is an airborne, downward-looking differential absorption lidar (DIAL) system capable of measuring water vapor concentration as well as aerosol backscatter with high horizontal and vertical resolution in the ABL. Here, we will demonstrate how the LASE data can be used to determine water vapor statistics and most of the water vapor budget terms in the ABL. This information can then be related to spatial variations in soil moisture and the surface energy budget. The extensive surface and aircraft in situ measurements conducted during SGP97 provide information on the ABL that cannot be retrieved from the LASE data alone and also offer an excellent opportunity to validate the remote water vapor budget measurements with LASE.

Senff, Christoph J.↗
NASA NTRS2010

Detailed Structure of the Tropical Upper Troposphere and Lower Stratosphere as Revealed by Balloon Sonde Observations of Water Vapor, Ozone, Temperature, and Winds During the NASA TCSP and TC4 Campaigns

We report on balloon sonde measurements of water vapor and ozone using the cryogenic frost point hygrometer and electrochemical concentration cell ozonesondes made at Alajuela, Costa Rica (10.0 N, 84.2 W) during two NASA airborne campaigns: the Tropical Convective Systems and Processes (TCSP) mission in July 2005 and the Tropical Composition, Clouds, and Climate Coupling Experiment (TC4), July - August 2007. In both campaigns we found an upper troposphere that was frequently supersaturated but no evidence that deep convection had reached the tropopause. The balloon sondes were complemented by campaigns of 4 times daily high-resolution radiosondes from mid-June through mid-August in both years. The radiosonde data reveal vertically propagating equatorial waves that caused a large increase in the variability of temperature in the tropical tropopause layer (TTL). These waves episodically produced cold point tropopauses (CPTs) above 18 km, yet in neither campaign was saturation observed above approx 380 K or 17 km. The averages of the water vapor minima below this level were 5.2 ppmv in TCSP and 4.8 ppmv in TC4, and the individual profile minima all lay at or above approx 360 K. The average minima in this 360 C380 K layer provide a better estimate of the effective stratospheric entry value than the average mixing ratio at the CPT. We refer to this upper portion of the TTL as the tropopause saturation layer and consider it to be the locus of the final dehydration of nascent stratospheric air. As such, it is the local equivalent to the tape head of the water vapor tape recorder.

Selkirk, Henry B.↗
NASA NTRS2009

On the Quality of the Nimbus 7 LIMS Version 6 Water Vapor Profiles and Distributions

This report describes the quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) water vapor (H2O) profiles of 1978/79 that were processed with a Version 6 (V6) algorithm and archived in 2002. The V6 profiles incorporate a better knowledge of the instrument attitude for the LIMS measurements along its orbits, leading to improvements for its temperature profiles and for the registration of its water vapor radiances with pressure. As a result, the LIMS V6 zonal-mean distributions of H2O exhibit better hemispheric symmetry than was the case from the original Version 5 (V5) dataset that was archived in 1982. Estimates of the precision and accuracy of the V6 H2O profiles are developed and provided. Individual profiles have a precision of order 5% and an estimated accuracy of about 19% at 3 hPa, 14% at 10 hPa, and 26% at 50 hPa. Profile segments within about 2 km of the tropopause are often affected by emissions from clouds that appear in the finite field-of-view of the detector for the LIMS H2O channel. Zonally-averaged distributions of the LIMS V6 H2O are compared with those from the more recent Microwave Limb Sounder (MLS) satellite experiment for November, February, and May of 2004/2005. The patterns and values of their respective distributions are similar in many respects. Effects of a strengthened Brewer-Dobson circulation are indicated in the MLS distributions of the recent decade versus those of LIMS from 1978/79. A tropical tape recorder signal is present in the 7-month time series of LIMS V6 H2O with lowest values in February 1979, and the estimated, annually-averaged "entry-level" H2O is 3.5 to 3.8 ppmv. It is judged that this historic LIMS water vapor dataset is of good quality for studies of the near global-scale chemistry and transport for pressure levels from 3 hPa to about 70 to 100 hPa.

Remsberg, E. E.↗
NASA NTRS1987

Measurements of mesospheric water vapor in 1984 and 1985 - Results and implications for middle atmospheric transport

The detailed results of ground-based mesospheric water vapor measurements obtained by microwave spectroscopy at the Jet Propulsion Laboratory (JPL) from December 1984 to April 1985 (JPL 1984/85), and an overview of results obtained the previous year from April to June 1984 are presented. The JPL 1984/85 spectral data appeared to contain an instrumental baseline curvature which was bracketed and removed. In general, the JPL 1984/85 results are in good agreement with those of previous measurements. They indicate water vapor mixing ratios between 6 and 8 ppmv at 60 or 65 km and falling off steeply with height above this point to values of less than 2 ppmv at 80 km. In addition, there is a large amount of day-to-day variability indicated in the data. A major result of the study is that it is found that both the observed vertical gradient of water vapor mixing ratio and its seasonal variation are consistent with the hypothesis that vertical transport time scales are smaller, perhaps by an order of magnitude, than values currently used in both one- and two-dimensional photochemical/dynamical models.

Bevilacqua, Richard M.↗
NASA NTRS1974

Water vapor diffusion membranes

The program is reported, which was designed to define the membrane technology of the vapor diffusion water recovery process and to test this technology using commercially available or experimental membranes. One membrane was selected, on the basis of the defined technology, and was subjected to a 30-day demonstration trial.

Holland, F. F., Jr.↗
NASA NTRS1976

Water vapor diffusion membrane development

A total of 18 different membranes were procured, characterized, and tested in a modified bench-scale vapor diffusion water reclamation unit. Four membranes were selected for further studies involving membrane fouling. Emphasis was placed on the problem of flux decline due to membrane fouling. This is discussed in greater details under "Summary and Discussion on Membrane Fouling Studies" presented in pages 47-51. The system was also investigated for low temperature application on wash-water where the permeated water is not recovered but vented into space vacuum.

Tan, M. K.↗
DOE OSTI2021

Water vapor oxidation of SiC layer in surrogate TRISO fuel particles

Under accidental conditions for high temperature gas-cooled reactors (HTGR), the SiC layer in tri-structural-isotropic (TRISO) fuel particles can be exposed to water vapor. In this study, oxidation behaviors of surrogate TRISO fuel particles were investigated in a He-20 vol% water vapor mixed atmosphere at temperatures up to 1600 °C. The growth of the crystalline oxide passivation layer with cracks and pores followed a parabolic law with time, where the maximum was 2.3 μm at 1600 °C. The oxide layer and the SiC surface under the oxide became flattened with increasing temperature, as a function of the silica viscosity and the diffusion path of water vapor. Volatilization of the oxide layer was analyzed using a mechanistic model that an inert gas in oxidizing atmospheres could influence the magnitude of volatilization. The fracture load and strength of the oxidized and thinned SiC layer were numerically estimated to decrease from 2.27 to 1.69 N and from 317 to 299 MPa, respectively, with the SiC thickness decrease from 35 to 32 μm. This prediction indicates that the oxidized SiC layer should retain fission products. Additionally, the mechanical integrity of each layer in the TRISO fuel particle after oxidation was evaluated. The results in this work provide important data for the safety analysis of accidental scenarios in HTGRs.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Satellite derived atmosphere water vapor as a tracer of large scale interactions between the atmosphere and ocean

Two water-vapor distributions and the accompanying circulation patterns which occurred over the North and South Atlantic Ocean during February 1979 are described. It is shown that scanning multichannel microwave radiometer observations from the Nimbus-7 satellite are used to remotely sense the vertically integrated atmospheric water vapor and liquid water, and the surface wind speed over the ocean and that they provide information on the ocean-atmosphere interaction. To provide evidence of the events revealed in the satellite observations, FGGE data are used.

Short, D. A.↗
NASA NTRS1973

Observations of water vapor ions at the lunar surface.

The Apollo 14 Suprathermal Ion Detector Experiment observed a series of bursts of 48.6 eV water vapor ions at the lunar surface during a 14-hr period on Mar. 7, 1971. The maximum flux observed was 100 million ions per sq cm per sec per sr. These ions were also observed at Apollo 12, 183 km to the west. Evaluation of specific artificial sources including the Apollo missions and the Russian Lunokhod leads to the conclusion that the water vapor did not come from a man-made source. Natural sources exogenous to the moon such as comets and the solar wind are also found to be inadequate to explain the observed fluxes. Consequently, these water vapor ions appear to be of lunar origin.-

Freeman, J. W., Jr.↗
NASA NTRS1992

Analysis of satellite-derived ozone and water vapor measurements

Research under this grant has involved analyses of satellite-derived measurements of water vapor and total ozone. Upper tropospheric water vapor data from the Nimbus 7 temperature-humidity infrared radiometer (THIR) 6.7 micron channel were analyzed by Fourier transformation to provide wavenumber spectra for a case of an upper level system over Europe. The power law spectrum for horizontal scales from 60 to several hundred km suggests that when convective cloud energy sources are not present, the enstrophy-cascading process (with variance proportional to the minus three power of wavenumber) may hold to much smaller scales than previously thought. Several investigations of the middle atmosphere (stratosphere and mesosphere) were also conducted. Slow atmospheric oscillations with periods of 1-2 months were investigated in total ozone measurements and in ionospheric data. Using one-point correlation maps and total ozone mapping spectrometer (TOMS) data, strong statistical evidence was found for the planetary-scale oscillations at these periods. A dipole-like pattern in the tropical equatorial Indian ocean-western Pacific region was documented, along with wavetrain-like patterns emanating into the extratropics. While attempting to follow the oscillations upward above stratosphere, oscillations were studied in ionospheric data (D-region radio wave absorption, in the upper mesosphere, around 80-90 km altitude). Cross-spectral analyses with solar flux data revealed that much of the observed 1-2 month variance in the ionospheric D-region was well correlated to solar variations. Further research has involved investigations of the photochemical lifetime of greenhouse gases methane and nitrous oxide. Using Nimbus 7 satellite data, a new analysis technique was employed to determine the lifetime of these gases in situ in the upper stratosphere. The lifetimes are found to be in good agreement with theoretical estimates.

Stanford, John L.↗
NASA NTRS1988

Vertical motion as inferred by the VAS 6.7 micron water vapor channel

The change of topography of the upper-most water vapor layer is used as a tracer to directly estimate vertical motion in subtropical atmospheres. An equation for vertical motion is derived using the relationship between 6.7-micron brightness temperature and the altitude of the upper layer of water vapor. This equation is used to estimate the vertical motion over the southeastern U.S. for July, 1984. The obtained values are compared to the vertical motion derived kinematically from radiosondes.

Stout, John↗
NASA NTRS1983

Water vapor profile retrievals from the HIRS/MSU sounder

The present physically based water vapor profile retrieval system for the HIRS/MSU sounding instrument is capable of producing accurate atmospheric and surface temperature retrievals, as well as accurate measurements of cloud fields on the basis of radiance values. In order to establish the extent of useful water vapor information in channels 8, 10, 11 and 12 of the HIRS instrument, studies have been conducted in which simultaneous temperature/humidity retrievals were performed on the basis of radiances simulated for clear and cloudy conditions.

Reuter, D.↗
NASA NTRS1990

A cryogenically cooled photofragment fluorescence instrument for measuring stratospheric water vapor

An instrument developed for high-resolution daytime measurements of water vapor in the stratosphere using the technique of photofragment fluorescence is examined. A detailed description of all aspects of the instrument, as well as the results of its first two flights, are presented. The main areas of concern were optical baffling, cryogen transfer, water vapor measurement without contamination, and a dual path absorption measurement. Results of the second flight test indicate that the problems of instrument and gondola contamination, identified in the first flight test, were solved. A signal-to-noise ratio of about 50:1 for 10 sec of averaging throughout the stratosphere is achieved, as well as an altitude resolution of better than 100 m.

Weinstock, Elliot M.↗
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.↗