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Cloud Structure Anomalies Over the Tropical Pacific During the 1997/98 El Niño: A Test for Two Climate Models

Lu, R.(a), Dong, B.(b), Potter, G.L.(c), and Cess, R.D.(d), Institute of Atmospheric Physics, Chinese Academy of Sciences (a), Hadley Centre for Climate Prediction and Research (b), Lawrence Livermore National Laboratory (c), State University of New York at Stony Brook (d)
Fourteenth Atmospheric Radiation Measurement (ARM) Science Team Meeting

We have compared two atmospheric general circulation models, HadAM3 and CAM2, to ERBE and CERES radiometric measurements at the TOA, as well as to zonal winds from the NCEP/NCAR reanalysis, for the tropical Pacific Ocean. It is found that HadAM3 reproduces the ERBE/CERES inferred changes in cloud vertical structure during the strong 1997/98 El Nino. Relative to normal years, these changes consist of lower clouds in the western portion of the tropical Pacific and higher in the eastern portion. Zonal winds from the NCEP/NCAR reanalysis demonstrate that these vertical structure changes are caused by a collapse of the Walker circulation, in turn caused by the lack of a zonal SST gradient during the El Nino. HadAM3 likewise produces a collapse of the Walker circulation. This demonstrates that the 1997/98 El, Nino serves as an important test of climate models and will help in using ARM TWP data to improve the models.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).