A comparison of two major Earth radiation budget data sets

Abstract

The Earth radiation budget data obtained from the Nimbus 7 Earth Radiation Budget (ERB) and the Earth Radiation Budget Experiment (ERBE) spacecraft missions are compared for several overlapping months during the period November 1984 to January 1986. The Nimbus 7 ERB data set starts in November 1978 and extends through October 1987 (9 years). The ERBE data set starts in November 1984 with the ERBS satellite, which was supplemented by the NOAA 9 in January 1985 and the NOAA 10 in September 1986. Data from both the ERBS and the NOAA 9 are presently being released to the scientific community. The principal aim of the ERBE project is to obtain improved measurements of the diurnal variations in the Earth radiation budget in order to derive accurate radiation budget products. On the Nimbus 7 ERB, only the wide field of view sensors have been active since July 1980. During the comparison period, both the ERBS and NOAA 9 had active wide field of view, medium field of view, and narrow field of view (scanner) sensors. Top of the atmosphere, colocated wide field of view (WFOV) measurements are compared to estimate relative biases. Then all the time‐ and space‐averaged products are compared. Each WFOV instrument has a shortwave and a total spectral channel. The outgoing longwave radiation is taken as the difference between the total and shortwave readings. The Nimbus 7 WFOV shortwave sensor reads about 2.5% higher than the ERBS sensor, while the Nimbus 7 total channel reads about 1% below the ERBS channel near midnight and about 1% above it near noon. A comparative study of the time‐ and space‐averaged data products for April, July, and October 1985 and January 1986 shows that the Nimbus 7 ERB global averages agree in the mean with the combined ERBS/NOAA 9 scanner values to within 0.16% in the outgoing longwave radiation and 0.03% in the albedo. The agreement of the combined ERBS/NOAA 9 WFOV products to the ERBS/NOAA 9 scanner products is 0.17% in the outgoing longwave radiation and 3.55% in the albedo. Certain fortuitous approximations in the time‐ and space‐averaging algorithms appear to have helped the agreement in the final mean Nimbus 7 and ERBE products. Monthly and regional differences are somewhat larger than for the 4‐month mean global values.

Long-term global distribution of earth's shortwave radiation budget at the top of atmosphere

“…On the other hand, published results (e.g. Kyle et al, 1990Kyle et al, , 1993Li et al, 1997;Yu et al, 1999;Ho et al, 2002) indicate significant discrepancies between model results and satellite data or even between different satellite data. In addition, global circulation models (GCMs) still have difficulties in computing the TOA SWRB components, especially under all-sky (clear plus cloudy sky) conditions (Harshvardhan et al, 1989;Kiehl et al, 1994;Ridout et al, 1994;Chen and Roeckner, 1996;Fowler et al, 2000;Loeb et al, 2002).…”

Global distribution of Earth's surface shortwave radiation budget

“…In the last two decades, a large number of studies estimating SRB have been published (e.g. Raschke et al, 1987;Darnell et al, 1988;Rossow and Lacis, 1990;Kyle at al., 1990;Stephens and Greenwald, 1991;Darnell et al, 1992;Hartmann, 1993;Li and Leighton, 1993;Kiehl et al, 1995;Rossow and Zhang, 1995;Whitlock et al, 1995;Fowler and Randall, 1996;Del Genio et al, 1996;Chen and Roeckner, 1996;Wild et al, 1998a, b;Yu et al, 1999). Gupta et al (1999) derived a 8-year (July 1983-June 1991 climatology of SRB by using satellite data from the ISCCP C-series, on a monthly mean basis.…”

Outgoing longwave radiation from the TOVS Pathfinder Path A data set

“…As indicated by previous studies [e.g., Kyle et al, 1990;Gruber et al, 1994], the differences among various OLR data sets may result from a combination of factors such as differences in instrumentation and calibration; spatial, temporal, and spectral sampling; and algorithms used in deriving the OLR.…”