Leading interannual variability modes of East Asian winter precipitation in CMIP5 general circulation models

摘要

This study examined the performances of 19 atmospheric general circulation models, which participated in Coupled Model Intercomparison Project 5 (CMIP5), while simulating East Asian winter (JFM) precipitation. The first 3 leading interannual variability modes of East Asian winter precipitation were obtained using the empirical orthogonal function (EOF) method. Results indicated that the observed first EOF mode, which accounted for 59% of the total variance and is ENSO related, represented a positive precipitation center over southern China. Specifically, the warm sea surface temperature (SST) in the equatorial central eastern Pacific induces an anomalous Philippine Sea anticyclone, and the increased southwesterly winds further transport anomalous water vapor to southern China, which causes more precipitation. EOF1 was well reproduced in the multimodel ensemble mean (MME), with a pattern correlation coefficient (PCC) of 0.84 and a temporal correlation coefficient (TCC) of 0.61. The observed EOF2 exhibited a north-south seesaw pattern, which may be forced by both the western Indian Ocean SST and the high-latitude wave train. The MME partially captured its spatial pattern (with a PCC of 0.48); however, it failed to reproduce its temporal variation (with a TCC of 0.17). The observed EOF3 exhibited an east-west dipole pattern, which was an Arctic Oscillation (AO)-related mode. In the negative AO phase, the strengthened East Asian trough at 500 hPa and the anomalous northerlies were observed to suppress precipitation over East Asia. However, almost all the models, including the MME, poorly simulated the temporal variation of EOF3 because the AO was considered to be an internal mode of the atmosphere.