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Wayne L. Darnell, Shashi K. Gupta, and W. Frank Staylor

Abstract

An extensive study has been carried out to validate a satellite technique for estimating downward longwave radiation at the surface. The technique, mostly developed earlier, uses operational sun-synchronous satellite data and a radiative transfer model to provide the surface flux estimates. The satellite-derived fluxes were compared directly with corresponding ground-measured fluxes at four different sites in the United States for a common one-year data period. This provided a study of seasonal variations as well as a diversity of meteorological conditions. Dome heating errors in the ground-measured fluxes were also investigated and were corrected prior to the comparisons. Comparison of the monthly averaged fluxes from the satellite and ground sources for all four sites for the entire year showed a correlation coefficient of 0.98 and a standard error of estimate of 10 W m−2. A brief description of the technique is provided, and the results validating the technique are presented.

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Shashi K. Gupta, Wayne L. Darnell, and Anne C. Wilber

Abstract

Several improvements have been made recently to the parameterization for surface longwave radiation described by Gupta. Model constants have been modified in order to use meteorological data from the International Satellite Cloud Climatology Project instead of from the TIROS Operational Vertical Sounder data, primarily to take advantage of the vastly superior cloud information available from the former. Additional modifications were made to improve the estimation of cloud effect in the presence of low-level clouds. The latter modifications reduced the systematic error of the overcast-sky fluxes from 10.0 to 1.7 W m−2 and the random error from ±18.9 to ±6.3 W m−2 when compared to the fluxes computed with a detailed radiative transfer model.

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Wayne L. Darnell, Shashi K. Gupta, and W. Frank Staylor

Abstract

A new technique is presented for generating downward longwave flux at the Earth's surface from satellite meteorological data and a radiative transfer model The technique was tested by using TIROS-N data from 41 passes over a ground site covering a period of one month. Satellite-derived fluxes were compared with those measured by a ground-based pyrgeometer during each overpass. The standard error of the satellite-derived fluxes relative to the mean ground-measured values was found to be 6.5%.

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Wayne L. Darnell, W. Frank Staylor, Shashi K. Gupta, and Frank M. Denn

Abstract

A technique is presented for estimating insulation at the Earth's surface using only sun-synchronous satellite data. The technique was tested by comparing the insolation results from year-long satellite datasets 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 m−2, or 2.7% of the average ground insulation value.

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