Comparison of Energy Source Estimates Derived from Atmospheric Circulation Data with Satellite Measurements of Net Radiation

Carl Fortelius Department of Meteorology, University of Helsinki, Helsinki, Finland

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Eero Holopainen Department of Meteorology, University of Helsinki, Helsinki, Finland

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Abstract

The distributions of the net sources of atmospheric dry and latent energy are evaluated by the residual technique using the reanalyzed ECMWF FGGE level IIIb data for February and July 1979. Their sum (i.e., the residual estimate of the source of total energy) is compared to simultaneous Nimbus-7 ERB estimates of the net radiation at the top of the atmosphere. Over land the estimated total energy source should be nearly equal to the net radiation.

The best agreement is found in July 1979 over the Northern Hemisphere middle latitudes, where monthly averages over large land areas agree to within 10 W m−2. Elsewhere, differences of up to 60 W m−2 occur for corresponding averages. Over low latitude continents, the residuals are generally too small over convectively active regions and too large over subsidence regions. A reason for this may be known deficiencies in the radiation parameterizations of the forecast model used in the data assimilation.

The distribution of latent heat sources, obtained from the circulation data, is compared with climatological estimates based on the one hand, on surface observations and, on the other hand, on rawinsonde data only. It appears that recent developments in data assimilation methods have improved the usefulness of The “aerological method.”

Abstract

The distributions of the net sources of atmospheric dry and latent energy are evaluated by the residual technique using the reanalyzed ECMWF FGGE level IIIb data for February and July 1979. Their sum (i.e., the residual estimate of the source of total energy) is compared to simultaneous Nimbus-7 ERB estimates of the net radiation at the top of the atmosphere. Over land the estimated total energy source should be nearly equal to the net radiation.

The best agreement is found in July 1979 over the Northern Hemisphere middle latitudes, where monthly averages over large land areas agree to within 10 W m−2. Elsewhere, differences of up to 60 W m−2 occur for corresponding averages. Over low latitude continents, the residuals are generally too small over convectively active regions and too large over subsidence regions. A reason for this may be known deficiencies in the radiation parameterizations of the forecast model used in the data assimilation.

The distribution of latent heat sources, obtained from the circulation data, is compared with climatological estimates based on the one hand, on surface observations and, on the other hand, on rawinsonde data only. It appears that recent developments in data assimilation methods have improved the usefulness of The “aerological method.”

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