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At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Vertical distribution of aerosol extinction cross section and inference of aerosol imaginary index in the troposphere by lidar technique

The paper reports on vertical profiles of aerosol extinction and backscatter in the troposphere which were obtained from multi zenith angle lidar measurements. It is reported that a direct slant path solution was found to be not possible due to horizontal inhomogeneity of the atmosphere. Attention is given to the use of a regression analysis with respect to zenith angle for a layer integration of the angle dependent lidar equation in order to determine the optical thickness and aerosol extinction-to-backscatter ratio for defined atmospheric layers and the subsequent evaluation of cross-section profiles.

Spinhirne, J. D.↗
NASA NTRS1980

Saturn - Tropospheric ammonia and nitrogen

Photochemical calculations based on recent data on the Saturn temperature structure and Lyman-alpha albedo indicate that detectable amounts of gaseous ammonia may exist between 20 and 35 km above the cloud tops. An instrument that might be able to observe this gas is the spectrometer on board the International Ultraviolet Explorer satellite. The calculations also yield a maximum nitrogen mixing ratio at the cloud tops between 1.8 x 10 to the -10th to 6 x 10 to the -8th by volume, depending upon the degree of supersaturation of ammonia and hydrazine. Even the lower limit could produce intense emissions if electrical discharges such as those observed on Jupiter by Voyager are also present on Saturn, or if high energy particles penetrate to the Saturnian troposphere.

Atreya, S. K.↗
NASA NTRS1981

Design, development, and field testing of Infrared Heterodyne Radiometer (IHR) for remote profiling of tropospheric and stratospheric species

The performance of a dual-channel infrared heterodyne radiometer, designed to remotely monitor the concentration and vertical distribution of selected atmospheric species, is described. Ground based solar viewing measurement using the IHR were performed at selected laser transitions for ammonia (NH3 and ozone O3). Flight tests were conducted aboard the Galileo II, NASA Ames CV-990, on the Latitude Survey Mission. Ozone was the selected atmospheric species for the airborne flight measurements because of the scientific interest in this atmospheric species, the availability of in situ monitors, the coordinated ozone measurements, and the availability of ground truth data. The IHS was operated in the solar viewing mode to determine ozone distributions in the stratosphere and in the nadir viewing mode to determine the ozone distribution in the troposphere. Airborne atmospheric propagation measurements also were carried out at selected CO2 laser transitions.

Lange, R.↗
NASA NTRS1981

Laser absorption spectrometer - Remote measurement of tropospheric ozone

The laser absorption spectrometer (LAS) is an airborne instrument able to perform remote measurement of trace atmospheric gases. The instrument uses a pair of carbon dioxide laser-heterodyne receiver systems that are directed downward from an airplane and determines gas concentration by the differential absorption method. Configured to measure tropospheric ozone, the LAS has been used in conjunction with another instrumented aircraft to test the accuracy of this method of measurement. A complete description of the instrument is presented, and the results of extensive flight testing are summarized.

Shumate, M. S.↗
NASA NTRS1980

Galilean satellite eclipse studies. II - Jovian stratospheric and tropospheric aerosol content

Aerosol profiles of the Jovian stratosphere and troposphere are presented using the Galilean satellite eclipse technique. The aerosol content is tenuous and varies with altitude, increasing rapidly with downward passage through the tropopause. The data indicate the presence of some aerosols of undetermined structure above the tropopause. An extended haze distribution is proposed, but the possibility that the stratospheric aerosol resides in a thin layer is not excluded.

Smith, D. W.↗
NASA NTRS1981

Correlative study of thermospheric gravity waves and tropospheric vorticity area index

Based on the occurrence frequency of wave-like structures in 23,691 individual measurements of thermospheric density, it is demonstrated that there is no significant hemispherical correlation between satellite-measured thermospheric wave-like structures and the tropospheric vorticity area index in the epoch 1974-1976. However, in the northern polar zone, (60-90 deg) N, wave occurrence frequency is greater for large values of the 500 mb vorticity area index.

Chiu, Y. T.↗
NASA NTRS1981

Estimation of the propagation delay through the troposphere from microwave radiometer data

Microwave propagation delay through the troposphere is studied as a means of estimating the adverse effect of atmospheric water vapor on the accuracy of measurements made with very long baseline interferometry. Vertical profiles of temperature and water vapor density were obtained from a total of 240 radiosonde launches taken simultaneously at three New England locations in 1974; all studies were made at the 19 and 22.2 GHz frequency operating range of the radiometers. The wet path length in the zenith direction could be estimated from the surface water vapor density to an accuracy of 5 cm for the summer data and 2 cm for winter data, and with the brightness temperatures, it could be estimated to an accuracy of 0.3 cm. Two dual-frequency radiometers were also used to determine the accuracy of prediction of the path length from real radiometry data. The rms error for the estimation of wet path length from surface meteorological parameters was 3.2 cm, and for the radiometer brightness temperatures the rms error was 1.5 cm.

Moran, J. M.↗
NASA NTRS1981

Long-wave baroclinic instability in the troposphere and stratosphere with spherical geometry

The most unstable normal modes are obtained for a global, quasi-geostrophic and spectral-form atmospheric model that includes wavenumbers one through six. In a first set of model calculations, the basic state represents Northern Hemisphere winter solstice conditions, whose long waves are deep modes having maximum kinetic energy in the stratosphere. These internal modes exist even in the presence of a stratospheric wind minimum, but propagate vertically into the stratosphere only north of this minimum, at the latitudes of the polar jet. The basic state for a second set of calculations is the axisymmetric solution corresponding to radiative equilibrium, with large vertical wind shear and all modes being essentially external, tropospheric Charney modes.

Straus, D. M.↗
NASA NTRS1981

Potential role of CS2 photooxidation in tropospheric sulfur chemistry

Absorption cross section measurements and model calculations indicate that CS2 photooxidation may be an important tropospheric sink for the CS2, giving a lifetime on the order of a week or two. If background CS2 levels are 10-20 pptv, then CS2 photooxidation may be an important global source of OCS as well.

Wine, P. H.↗
NASA NTRS1981

The transport of photochemical pollutants to the background troposphere

The considered investigation is concerned with the phenomena occurring as a chemically reacting plume, with specific initial concentrations of NO, NO2, O3, and hydrocarbons, emerges from an urban area and is advected to the background troposphere. A better understanding of the global NOx and hydrocarbon budgets can be realized by determining the fractions of NOx and hydrocarbons that are transported to distances far enough to be considered background. The investigation makes use of a 56-step, lumped kinetic mechanism for photochemical smog, which includes current information on pertinent chemical reactions and rate constants for the reactions.

Bazzell, C. C.↗
NASA NTRS1981

Tropospheric chemistry - A global perspective

Processes that affect the concentration of tropospheric OH are considered, taking into account linkages between the chemistry of OH and the chemistry of H, HO2, and H2O2. A review is presented of observational data of special relevance to OH, notably the distributions of CO, CH4, O3, H2O, HNO3, NO, and NO2. Most of the results presented in connection with the description of the model were obtained by solving time-dependent continuity equations. Rates for photolytic processes were allowed to vary diurnally with insolation. It is found that a well-calibrated and reliable model for OH places important constraints on global budgets for a variety of gases including CH4, H2, and CH3Cl in addition to CO. Accurate measurements of species such as CH3CCl3 can provide valuable checks on global models that must integrate over a variety of atmospheric conditions. However, emission rates for the relevant gases must be adequately quantified.

Logan, J. A.↗
NASA NTRS1981

The distribution of carbon monoxide and ozone in the free troposphere

The two-dimensional distributions of CO and O3 in the free troposphere during July and August, 1974, are discussed. The data confirm the previous findings that both of these gases are considerably more abundant in the northern hemisphere, but the degree of the asymmetry is somewhat different from what had been reported previously, especially for CO. When examined with respect to other available data sets, the conclusion is drawn that a pronounced seasonal cycle exists for CO in both hemispheres which may be driven by the likely seasonal cycle of the OH radical. The data also indicate that CO concentrations exhibit significant variability with height in the northern hemisphere, whereas southern hemispheric concentrations are quite constant with altitude except in cases where interhemispheric exchange of air may be occurring. A discussion on the vertical and horizontal transport processes inferred from the CO and O3 measurements is presented. The possible interdependence of the photochemical cycles of these two trace gases is also discussed.

Seiler, G.↗
NASA NTRS1982

Effects of diabatic heating on the ageostrophic circulation of an upper tropospheric jet streak

Interaction between the mass circulation within a mesoscale convective complex (MCC) and a direct mass circulation in the entrance region of an upper tropospheric polar jet streak was examined within the isentropic structure to investigate mechanisms responsible for linking these two scales of motion. The results establish that latent heating in the MCC modifies the direct mass circulation in the jet streak entrance region through the diabatically induced components of ageostrophic motion analyzed within isentropic coordinates. Within the strong mesoscale mass circulation of each MCC, strong horizontal mass flux convergence into the MCC at low levels is balanced by strong horizontal mass flux divergence away from the convergence at upper levels. Locations of large diabatic heating rates correspond well to the MCC position for each case; diabatic heating forces the upward vertical branch for the mesoscale mass circulation.

Keyser, D. A.↗
NASA NTRS1982

Initial studies of middle and upper tropospheric stratiform clouds

The spatial and temporal occurrence of cloud layers, the development of a physical-numerical model to simulate the life cycles of tropospheric cloud layers, and the design of an observational program to study the properties of these layers are described.

Cox, S. K.↗
NASA NTRS1982

Characteristics of middle and upper tropospheric clouds as deduced from rawinsonde data

The static environment of middle and upper tropospheric clouds is characterized. Computed relative humidity with respect to ice is used to diagnose the presence of cloud layer. The deduced seasonal mean cloud cover estimates based on this technique are shown to be reasonable. The cases are stratified by season and pressure thickness, and the dry static stability, vertical wind speed shear, and Richardson number are computed for three layers for each case. Mean values for each parameter are presented for each stratification and layer. The relative frequency of occurrence of various structures is presented for each stratification. The observed values of each parameter and the observed structure of each parameter are quite variable. Structures corresponding to any of a number of different conceptual models may be found. Moist adiabatic conditions are not commonly observed and the stratification based on thickness yields substantially different results for each group.

Starr, D. D. O.↗
NASA NTRS1982

A middle and upper tropospheric cloud model

The interplay of the various physical processes involved in the formation, maintenance, and decay of middle and upper tropospheric stratiform clouds is discussed. Ice phase fair weather cloud forms are considered. Simulations of cirriform clouds which attempt to incorporate the physical processes in an interactive manner were performed. A two dimensional time dependent Eulerian numerical model, which incorporates all of the important physical processes in a simplified way, is employed to investigate the role of these processes in the evolution of a cloud in an isolated atmospheric layer. Physical parameters considered are the eddy viscosity and the thermal, water vapor, and ice water eddy diffusivities.

Source record↗
NASA NTRS1982

Tropospheric Passive Remote Sensing

The long term role of airborne/spaceborne passive remote sensing systems for tropospheric air quality research and the identification of technology advances required to improve the performance of passive remote sensing systems were discussed.

Keafer, L. S., Jr.↗