Global shortwave energy budget at the earth's surface from ERBE observations
- California Space Institute, Scripps Institution of Oceanography, La Jolla, CA (United States)
- Univ. of California, Santa Barbara, CA (United States)
A method is proposed to compute the net solar (shortwave) irradiance at the earth's surface from Earth Radiation Budget Experiments (ERBE) data from S4 data (monthly averaged broadband planetary albedo). Net surface shortwave irradiance is obtained for the shortwave irradiance incident at the top of the atmosphere (known) by subtracting both the shortwave energy flux reflected by the earth-atmosphere system (measured) and the energy flux absorbed by the atmosphere (modeled). Precalculated atmospheric- and surface-dependent functions that characterize scattering and absorption in the atmosphere are used along with four surface types: ocean, vegetation, desert, snow/ice. Over the tropical Pacific Ocean, the estimates compare well with the International Satellite Cloud Climatology Project (ISCCP) B3 data. Over snow/ice, vegetation, and desert no comparison is made with other satellite-based estimates, but theoretical calculations using the discrete ordinate method suggest that over highly reflective surfaces (snow/ice, desert) the model may substantially overestimate the absorbed solar energy flux at the surface, especially when clouds are optically thick. The monthly surface shortwave irradiance fields produced for 1986 exhibit the main features characteristic of the earth's climate. Our values are generally higher than Esbensen and Kushnir's by as much as 80 W m[sup [minus]2] in the tropical oceans. The difference between clear-sky and actual irradiances normalized to top-of-atmosphere clear-sky irradiance is higher in the midlatitude regions of storm tracks than in the intertropical convergence zone (ITCZ), suggesting the higher cloud coverage in midlatitudes is more effective at reducing surface shortwave irradiance than opaque, convective, sparser clouds in the ITCZ. Surface albedo estimates are realistic, generally not exceeding 0.06 in the ocean, as high as 0.9 in polar regions, and reaching 0.5 in the Sahara and Arabian deserts. 33 refs., 11 figs., 2 tabs.
- OSTI ID:
- 7266125
- Journal Information:
- Journal of Climate; (United States), Vol. 7:2; ISSN 0894-8755
- Country of Publication:
- United States
- Language:
- English
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