1990 .

(3 publications)

R. D. Cess, G. L. Potter, J. P. Blanchet, G. J. Boer, A. D. Del Genio, M. DéQué, V. Dymnikov, V. Galin, W. L. Gates, S. J. Ghan, J. T. Kiehl, A. A. Lacis, H. Le Treut, Z.-X. Li, X.-Z. Liang, B. J. McAvaney, V. P. Meleshko, J. F. B. Mitchell, J.-J. Morcrette, D. A. Randall, L. Rikus, E. Roeckner, J. F. Royer, U. Schlese, D. A. Sheinin, A. Slingo, A. P. Sokolov, K. E. Taylor, W. M. Washington, R. T. Wetherald, I. Yagai, and M.-H. Zhang. Intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models. Journal of Geophysical Research, 95:16, September 1990. [ bib | DOI | ADS link ]

The need to understand differences among general circulation model projections of CO2-induced climatic change has motivated the present study, which provides an intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models. This intercomparison uses sea surface temperature change as a surrogate for climate change. The interpretation of cloud-climate interactions is given special attention. A roughly threefold variation in one measure of global climate sensitivity is found among the 19 models. The important conclusion is that most of this variation is attributable to differences in the models' depiction of cloud feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as reliable climate predictors. It is further emphasized that cloud feedback is the consequence of all interacting physical and dynamical processes in a general circulation model. The result of these processes is to produce changes in temperature, moisture distribution, and clouds which are integrated into the radiative response termed cloud feedback.

L. Picon and M. Desbois. Relation between METEOSAT Water Vapor Radiance Fields and Large Scale Tropical Circulation Features. Journal of Climate, 3:865-876, August 1990. [ bib | DOI | ADS link ]

Mean monthly images from the water vapor channel of METEOSAT characteristically contain large-scale spatial structures, especially in tropical regions. The aim of this paper is to establish connections between these structures and large-scale circulation features. For this purpose, statistical relationships between radiances and some meteorological parameters provided by ECMWF analyses are studied.Temporal correlations are computed for two sizes of regions, in order to compare temporal changes associated with both large-scale circulations and smaller scale systems. The correlations obtained are poor, suggesting that the chosen parameters are not well related at short time scales.Temporal averages appear more suitable for these comparisons. As expected, the mean relative humidity yields the best correlation with the mean water vapor radiances. A (weaker) relationship exists also with mean dynamic fields: large water vapor radiances are almost always related to subsidence in the middle troposphere, divergence near the surface, and convergence in the upper troposphere. However, there is regional variability in the results., one explanation may be different contributions from horizontal advecion and vertical motions to the humidity of the middle troposphere.

L. Fairhead and P. Bretagnon. An analytical formula for the time transformation TB-TT. Astronomy Astrophysics, 229:240-247, March 1990. [ bib | ADS link ]

An analytical formula for the time transformation TB-TT valid over a few thousand years around J2000 has been computed with an accuracy at the 1 ns level. The 127 coefficients presented in this paper provide a formula accurate at the 100 ns level. The numerical and analytical procedures to compute this transformation are discussed and compared. It is noted that these procedures cannot fully comply with recommendations 5 of the 1976 IAU meeting. Furthermore, these procedures yield different units for the corresponding TB time scales. It is verified that this transformation is independent of the two parameterized post Newtonian parameters gamma and beta and of the three most commonly used coordinate systems (isotropic, standard-Schwarzschild, Painleve) at least the 1 ns level.