engleski

Climate diagnostics of the ECMWF AMIP-2 simulations

Some results from the two integrations with the ECMWF model participating in the AMIP-2 project are presented and discussed. The model was integrated for over 20 years at two horizontal resolutions, T63 and TL159. In the vertical, there were 60 levels, extending to 0.1 mb. Most of the results are verified against ECMWF re-analysis data, ERA-15. For many parameters, the model was able to reproduce the DJF and JJA climatology fields reasonably well. However, some well known ECMWF model systematic deficiencies in the extended range are also seen in the AMIP-2 climatology, e.g. the intensification of the northern hemisphere DJF westerlies and the overestimation of precipitation within the ITCZ and in the winter storm tracks. The interannual variation was generally well reproduced in the tropics for years with strong ENSO signal. But even here there are exceptions - one being the overestimation of the tropical positive precipitation anomalies. In the extratropics, interannual variability is generally poor, indicating that in the AMIP-type experiments ensembles of integrations would be also necessary. Though the difference between the two resolutions is relatively small on average, larger differences were found in the stratosphere for some parameters indicating that long integrations including stratospheric processes may require special care.

climate; ECMWF; AMIP; extended range

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