Engineering topics

Gupta, Shashi K.

Publications and source records attributed to Gupta, Shashi K..

26 records · Page 2

NASA NTRS1992

Seasonal variation of surface radiation budget derived from International Satellite Cloud Climatology Project C1 data

Surface radiation budget data are presented for the midseasonal months of July and October of 1983 and January and April of 1984. These data allow the examination of geographical and seasonal variations of the entire surface radiation budget from pole to pole. The latest flux estimation techniques have been used along with data from the International Satellite Cloud Climatology Project and the Earth Radiation Budget Experiment. Regional, zonal, and hemispheric distributions of the downward and net components of both shortwave and longwave fluxes and of the net total surface fluxes are determined. Seasonal flux variation per region, expressed as flux range, is illustrated for these components also. The estimated fluxes appear to be accurate to about 16 W/sq m on a global average, based on sensitivity analyses and comparisons with ground data. An analysis of flux errors showed that most of the error was attributable to errors in input data.

Darnell, Wayne L.↗

NASA NTRS1990

Surface radiation budget - Current perspective

The surface radiation budget of the earth is important in climate research because it gives an understanding of the distribution of solar and IR radiation exchanges at the surface. Data on the distribution and exchange of these surface radiations are needed over the entire earth on a long-term basis. Global satellite data, coupled with highly developed models, now provide estimates of the surface radiation budget which are near the accuracy required for climate research. A description of surface radiation research, its current state, and planned programs are presented.

Darnell, Wayne L.↗

NASA NTRS1990

Longwave cloud radiative forcing at the surface from ISCCP-C1 data

A method for deriving one component of the total cloud forcing picture, namely, the LW cloud forcing at the surface, is presented. The method is based on a validated radiative transfer technique and utilizes meteorological data available from the International Satellite Cloud Climatology Project. The radiative transfer model used was validated earlier and the TOVS-derived temperature and water vapor data used were generally reasonable. On a monthly-average basis, random error was estimated to be in the 5-10 W/sq m range, but biases as large as 10-20 W/sq m can occur in some regions. The lack of information on cloud-base heights were found to be the largest source of errors in the models and the meteorological data.

Gupta, Shashi K.↗

NASA NTRS1990

Global correlations for surface radiation studies

This study demonstrates a strong correlation between surface absorbed shortwave flux and top-of-the-atmosphere net shortwave flux. This technique permits determination of absorbed shortwave radiation at the surface without knowledge of the surface albedo.

Wilber, Anne C.↗

NASA NTRS1990

Sensitivity of surface radiative fluxes to meteorological parameter errors

A parameterized radiative transfer model is employed to estimate longwave fluxes, while shortwave fluxes are estimated with a broadband absorption and scattering technique. Meteorological parameters of surface radiative fluxes are the profiles of temperature and cloud cover, ozone, water vapor and aerosols. A sensitivity study is presented to estimate the magnitudes of biases in the computed fluxes resulting from the biases in the satellite meteorological data.

Ritchey, Nancy A.↗

NASA NTRS1990

Global surface radiation flux results for all seasons using ISCCP-C1 data

Algorithms have been developed at the Langley Research Center to estimate fluxes for all of the surface radiation components utilizing the new International Satellite Cloud Climatology Project (ISSCP) C1 data and grid system. These surface radiation budget data are the first all-component flux set encompassing the entire globe, based on satellite-derived C1 meteorological data. A description of the input data and the algorithms utilized, examples of the global flux results, discussion of how the current fluxes compare with ground-truth fluxes, and remarks on errors in the current flux estimates are presented.

Darnell, Wayne L.↗

NASA NTRS1989

A parameterization for longwave surface radiation from sun-synchronous satellite data

A parameterization is presented for computing downward, upward, and net longwave radiation at the earth's surface using data from NOAA sun-synchronous satellites. The parameterization is applied to satellite soundings for April, 1982 over a large region of the tropical Pacific Ocean. Sensitivity studies were used to estimate the random and systematic errors in computed fluxes due to probable errors in TOVS-derived parameters. It is suggested that large biases in the results due to errors in TOVS-derived parameters may be corrected with data from the International Satellite Cloud Climatology Project.

Gupta, Shashi K.↗

NASA NTRS1988

Estimation of surface insolation using sun-synchronous satellite data

A technique is presented for estimating insolation at the earth's surface using only sun-synchronous satellite data. The technique was tested by comparing the insolation results from year-long satellite data sets with simultaneous ground-measured insolation taken at five continental United States sites. Monthly average insolation values derived from the satellite data showed a standard error of 4.2 W/sq m, or 2.7 percent of the average ground insolation value.

Darnell, Wayne L.↗