摘要
This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.
This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves （CCEWs）, including mixed Rossby-gravity （MRG） and tropical depression-type （TD-type） waves, based on the twentieth century experiments of 18 global climate mod- els （GCMs） from the Coupled Model Intercomparison Project phase 3 （CMIP3）. The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced. The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations, indi- cating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened. This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation. The mean precipitation in April and May shows a double-ITCZ problem, and the horizontal resolution is important to the delayed seasonal transition of wave activity. Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone （TC） geneses, the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs, namely, a delayed and shortened TC season in the northern hemisphere.
基金
supported financially by the National Basic Research Program of China (Grant No.2010CB950403)
the National Natural Science Foundation of China (Major Research,Grant No. 40890151
Grant Nos.40921160379 and 41105047)
supported by the National Science Council (Grant No. NSC98-2745-M-001-005-MY3)
supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy
