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Wang, P.-H.

Publications and source records attributed to Wang, P.-H..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Upper Stratospheric Temperature Climatology Derived from SAGE II Observations: Preliminary Results

This study shows that the temperature information in the upper stratosphere can be derived from the SAGE II 385-mn observations. The preliminary results indicate that the zonal mean temperature increases with altitude below 50 km and decreases above 50 km. At 50 km, a regional maximum of 263 K is located in the tropics, and a minimum of 261 K occurs in the subtropics in both hemispheres. The derived long-term temperature changes from 1985 to 1997 reveal a statistically significant negative trend of -2 to -2.5 K/decade in the tropical upper stratosphere and about -2 K/decade in the subtropics near the stratopause. At latitudes poleward of 50, the results show a statistically significant positive trend of about 1 K/decade in the upper stratosphere. The preliminary results also show large annual temperature oscillations in the extratropics with a maximum amplitude of approx. 8 K located at about 44 km near 50 in both hemispheres during local summer. In addition, the semiannual oscillation is found to be a maximum in the tropics with a peak amplitude of approx. 3.3 K located at about 42 km during the equinox.

Wang, P.-H.↗
NASA NTRS1998

Atmos/Atlas 3 Infrared Profile Measurements of Clouds in the Tropical and Subtropical Upper Troposphere

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 micron region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (/km) in microwindows at 831, 957, and 1204/cm have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 gm is estimated from the smallest ice crystals observed in the 8-12 micron region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 micron shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3.

Rinsland, C. P.↗
NASA NTRS1998

Atmos/Atlas 3 Infrared Profile Measurements of Trace Gases in The November 1994 Tropical and Subtropical Upper Troposphere

Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01/cm resolution infrared solar occultation spectra recorded between latitudes of 5.3degN and 31.4degN. The observations were obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 3 shuttle flight, 3-12 November 1994. Elevated mixing ratios below the tropopause were measured for these gases during several of the occultations. The positive correlations obtained between the simultaneously measured mixing ratios suggest that the enhancements are likely the result of surface emissions, most likely biomass burning and/or urban industrial activities, followed by common injection via deep convective transport of the gases to the upper troposphere. The elevated levels of HCN may account for at least part of the "missing NO," in the upper troposphere. Comparisons of the observations with values measured during a recent aircraft campaign are presented.

Rinsland, C. P.↗
NASA NTRS1998

ATMOS/ATLAS 3 Infrared Profile Measurements of Clouds in the Tropical and Subtropical Upper Troposphere

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 micron region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (/km) in microwindows at 831, 957, and 1204/cm have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 microns is estimated from the smallest ice crystals observed in the 8-12 gm region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 microns shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3.

Rinsland, C. P.↗
NASA NTRS1995

Comparing Simultaneous Stratospheric Aerosol and Ozone Lidar Measurements with SAGE 2 Data after the Mount Pinatubo Eruption

Stratospheric aerosol and ozone profiles obtained simultaneously from the lidar station at the University of L'Aquila (42.35 deg N, 13.33 deg E, 683 m above sea level) during the first 6 months following the eruption of Mount Pinatubo are compared with corresponding nearby Stratospheric Aerosol and Gas Experiment (SAGE) 2 profiles. The agreement between the two data sets is found to be reasonably good. The temporal change of aerosol profiles obtained by both techniques showed the intrusion and growth of Pinatubo aerosols. In addition, ozone concentration profiles derived from an empirical time-series model based on SAGE 2 ozone data obtained before the Pinatubo eruption are compared with measured profiles. Good agreement is shown in the 1991 profiles, but ozone concentrations measured in January 1992 were reduced relative to time-series model estimates. Possible reasons for the differences between measured and model-based ozone profiles are discussed.

Yue, G. K.↗
NASA NTRS1994

Validation of stratospheric aerosol and gas experiments 1 and 2 satellite aerosol optical depth measurements using surface radiometer data

The stratospheric aerosol measurement 2, stratospheric aerosol and gas experiment (SAGE) 1, and SAGE 2 series of solar occultation satellite instruments were designed for the study of stratospheric aerosols and gases and have been extensively validated in the stratosphere. They are also capable, under cloud-free conditions, of measuring the extinction due to aerosols in the troposphere. Such tropospheric extinction measurements have yet to be validated by appropriate lidar and in situ techniques. In this paper published atmospheric aerosol optical depth measurements, made from high-altitude observatories during volcanically quiet periods, have been compared with optical depths calculated from local SAGE 1 and SAGE 2 extinction profiles. Surface measurements from three such observatories have been used, one located in Hawaii and two within the continental United States. Data have been intercompared on a seasonal basis at wave-lenths between 0.5 and 1.0 micron and found to agree within the range of measurement errors and expected atmospheric variation. The mean rms difference between the optical depths for corresponding satellite and surface measured data sets is 29%, and the mean ratio of the optical depths is 1.09.

Kent, G. S.↗
NASA NTRS1994

Stratospheric aerosol acidity, density, and refractive index deduced from SAGE 2 and NMC temperature data

Water vapor concentrations obtained by the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and collocated temperatures provided by the National Meteorological Center (NMC) from 1986 to 1990 are used to deduce seasonally and zonally averaged acidity, density, and refractive index of stratospheric aerosols. It is found that the weight percentage of sulfuric acid in the aerosols increases from about 60 just above the tropopause to about 86 at 35 km. The density increases from about 1.55 to 1.85 g/cu cm between the same altitude limits. Some seasonal variations of composition and density are evident at high latitudes. The refractive indices at 1.02, 0.694, and 0.532 micrometers increase, respectively, from about 1.425, 1.430, and 1.435 just above the tropopause to about 1.445, 1.455, and 1.458 at altitudes above 27 km, depending on the season and latitude. The aerosol properties presented can be used in models to study the effectiveness of heterogeneous chemistry, the mass loading of stratospheric aerosols, and the extinction and backscatter of aerosols at different wavelengths. Computed aerosol surface areas, rate coefficients for the heterogeneous reaction ClONO2 + H2O yields HOCl + HNO3 and aerosol mass concentrations before and after the Pinatubo eruption in June 1991 are shown as sample applications.

Yue, G. K.↗
NASA NTRS1993

Background stratospheric aerosol and polar stratospheric cloud reference models

A global aerosol climatology is evolving from the NASA satellite experiments SAM II, SAGE I, and SAGE II. In addition, polar stratospheric cloud (PSC) data have been obtained from these experiments over the last decade. An undated reference model of the optical characteristics of the background aerosol is described and a new aerosol reference model derived from the latest available data is proposed. The aerosol models are referenced to the height above the tropopause. The impact of a number of volcanic eruptions is described. In addition, a model describing the seasonal, longitudinal, and interannual variations in PSCs is presented.

Mccormick, M. P.↗
NASA NTRS1987

Validation of SAM 2 and SAGE satellite

Presented are the results of a validation study of data obtained by the Stratospheric Aerosol and Gas Experiment I (SAGE I) and Stratospheric Aerosol Measurement II (SAM II) satellite experiments. The study includes the entire SAGE I data set (February 1979 - November 1981) and the first four and one-half years of SAM II data (October 1978 - February 1983). These data sets have been validated by their use in the analysis of dynamical, physical and chemical processes in the stratosphere. They have been compared with other existing data sets and the SAGE I and SAM II data sets intercompared where possible. The study has shown the data to be of great value in the study of the climatological behavior of stratospheric aerosols and ozone. Several scientific publications and user-oriented data summaries have appeared as a result of the work carried out under this contract.

Kent, G. S.↗
NASA NTRS1985

Variations in stratospheric aerosol optical depth during northern warmings

In this paper, the properties of the stratospheric aerosol optical depth (above 50 mbar) have been studied by using aerosol extinction profiles (at 1 micron) derived from the Stratospheric Aerosol Measurement and Stratospheric Aerosol and Gas Experiment (SAGE) during warming periods in the Northern Hemisphere. It is shown that, during the disturbed periods in winter, low values of aerosol optical depth (less than 0.0002) are found within the low-pressure system(s) (at the 30-mbar pressure surface), while high values are found outside. Similar characteristics are found to exist for the simultaneously observed SAGE O3 and NO2 columnar density distributions. Strong longitudinal gradients are shown with the low values within and wherever the vortex exists. This characteristic is maintained during and after the circumpolar vortex is disturbed, even after breakdown, indicating an isolation of the material within the vortex.

Wang, P.-H.↗
NASA NTRS1985

A study on radiative damping of planetary waves utilizing stratospheric observations

Satellite ozone observations made by the Stratospheric Aerosol and Gas Experiment (SAGE) and corresponding meteorological temperature data are used to study the radiative damping processes associated with planetary waves during stratospheric warmings. Ramanathan's model has been adapted for the radiative heating and cooling calculations. The derived infrared damping coefficients, based on observed stratospheric ozone and temperature, are compared with the Newtonian cooling coefficients of Dickinson and Fels. It is also shown that the negative correlation between temperature and ozone solar heating in the upper stratosphere accelerates the damping rate due to infrared cooling alone, in agreement with the theoretical analysis and an earlier report based on observations. In addition, it is also found in this analysis that the phase relationship between ozone and solar heating waves is characterized by its behavior in three distinct layers. In the regions above about 2 mb and also below about 10 mb, the waves are closely in-phase. Between approximately 2 and 10 mb, they show a departure from the in-phase relationship which can be attributed to the so-called 'opacity effect'. This effect significantly determines the magnitude of radiative damping.

Ghazi, A.↗
NASA NTRS1985

Behavior of zonal mean aerosol extinction ratio and its relationship with zonal mean temperature during the winter 1978-1979 stratospheric warming

The behavior of the zonal mean aerosol extinction ratio in the lower stratosphere near 75 deg N and its relationship with the zonal mean temperature during the January-February 1979 stratospheric sudden warming have been investigated based on the satellite sensor SAM II (Stratospheric Aerosol Measurement) and auxiliary meteorological measurements. The results indicate that distinct changes in the zonal mean aerosol extinction ratio occurred during this stratospheric sudden warming. It is also found that horizontal eddy transport due to planetary waves may have played a significant role in determining the distribution of the zonal mean aerosol extinction ratio.

Wang, P.-H.↗
NASA NTRS1985

Variations of radiative heating/cooling in the stratosphere as revealed by satellite observations

Ozone observations made by Stratospheric Aerosol and Gas Experiment (SAGE) and meteorological temperature data are used to study the coupling of radiation and dynamics in the stratosphere. Both radiative heating and cooling rates are calculated using the observations as a function of altitude, longitude, latitude, and season. Fourier analysis of heating/cooling rates is performed to gain an understanding of the radiation-planetary wave interactions. High correlation is seen to exist between solar heating and the temperature distribution of the upper stratosphere. Radiative damping coefficients are derived and it is found that the coupling between ozone and temperature can produce significant variations in the damping rate which, in turn, critically depends on the vertical structure of the planetary waves.

Wang, P.-H.↗
NASA NTRS1985

SAGE studies of the waves and eddy fluxes of ozone and temperature near 55 deg during the late February 1979 stratospheric warming

Ozone data from the Stratospheric Aerosol and Gas Experiment have been used in conjunction with meteorological information to study the waves and eddy fluxes of ozone and temperature near 55 deg N during the late February 1979 stratospheric warming. The results indicate an intense poleward eddy ozone transport in the altitude range between approximately 24 and 38 km, and an equatorward transport above an altitude of about 38 km. It is found that this equatorward eddy ozone transport in the upper stratosphere was accompanied by a poleward eddy heat transport, as expected on the basis of the ozone photochemistry. The results also indicate that the phase relationship between ozone and temperature waves agrees qualitatively with existing model analyses.

Wang, P.-H.↗
NASA NTRS1982

Retrieval of aerosol characteristics from scattering and extinction measurements

The present investigation is concerned with a versatile inversion code which is capable of retrieving profiles of aerosol size distributions and concentrations from multiwavelength satellite measurements of either the scattered radiance from the earth's sunlit atmosphere in both the limb-viewing mode and downward-viewing mode, or the extinction of direct solor radiation by the earth's atmosphere. The inversion code in its present form is a composite of three subcodes. The inversion code is composed of several module algorithms for treating the inverse problem in radiative transfer through a scattering and absorbing aerosol atmosphere, which is vertically inhomogeneous, spherical, and which takes into account multiple scattering and surface albedo effects. The inversion code has been applied and tested for a number of remote sensing techniques. Examples are given concerning the retrieval results for the vertical profiles of aerosol size distribution and concentation.

Deepak, A.↗
NASA NTRS1981

General formulation of optical paths for large zenith angles in the earth's curved atmosphere

Formulas that can be used to determine the optical path between two points along an atmospheric ray path are derived for the case when the local zenith angle of the ray path is larger than 70 deg. For angles less than 70 deg, these formulas reduce to the airmass function; viz., the secant of the zenith angle. The formulation presented in this paper is general enough to be applicable to a wide variety of atmospheric conditions, such as spherical and nonspherical atmospheres, and vertically and horizontally homogeneous as well as inhomogeneous atmospheres. A formulation for the case when atmospheric refraction is important also is presented here.

Wang, P.-H.↗