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By comparing the model outputs of IAP AGCM4 with the NCEP2 reanalysis data during 1979-2008, we evaluate the models performance in simulating the intraseasoanl variation of East Asian summer monsoon (EASM).It is shown that the model simulates the basic features of the observed monsoon circulation and rainfall in East Asia, together with the intraseasonal variation of EASM characterized by two northward jumps of western Pacific subtropical high (WPSH).There are, however, some discrepancies in the model: (1) The model tends to overestimates the intensity of WPSH by 20gpm owing to a higher air temperature in the lower and middle troposphere in the model, leading to insufficient summer rainfall over East Asia and western Pacific.(2) The WPSH in the model extends too far northward, as a result, the model fails to simulate the rain-belt in south China during May and June.In addition, the simulated EASM tends to retreat one month later than the observation due to a later establishment of Siberian high in the model.(3) The timing of two northward jumps of WPSH in the model is not coincident with the observation, with a later jump by two pentads for the first time and an earlier jump by one pentad for the second one, i.e., the duration between the two jumps is shorter than the observation.This error is partly due to that, in the atmospheric model driven by the observed sea surface temperature, the oscillating period of convection in the western Pacific warm pool is shorter.It is therefore concluded that air-sea interaction in the western Pacific is important for predicting the intraseasonal oscillation of EASM.