Study On The Influence And Mechanisms Of Indian Ocean Dipole And The Atlantic Equatorial Mode On The Precipitation Of China

In this paper, we use observational SST. precipitation, atmospheric circulation variables from the reanalyses of the ERA-20C. winter SST variation patterns in the tropical western Pacific related to the tropical Indian Ocean SST Dipole (IOD) and their impacts on precipitation of China were studied. Two kinds of SSTA patterns were found: a regional unanimous warm/cold pattern and a dipole mode with the opposite SST anomalies in the western side to the east side of the region. The two kinds of SST pattern both favor winter precipitation suppression in southeastern China, but the domain size with the impact is different. The unanimous SST pattern affects a larger region from south China to the middle and lower reaches of Yangtze River northward. The impact of the SST dipole pattern is only confined to South China, leading to less rainfall in South China but more rainfall in the middle and lower reaches of Yangtze River. The correspondent atmospheric circulation anomalies can explain these rainfall anomalies. Although an anomalous cyclone occurs over the Philippine Sea in both the cases, its strength and location are different. The cyclone forced by the unanimous warm SST pattern is stronger, thus the anomalous westerly and northeasterly in the rear extends to a wider region,leading to a dry in a larger domain. It contrast, the cyclone forced by the dipole pattern is weaker and the anomalous easterly and northeasterly is more confined,leading to a dry just confined in southern China. The sensitive experiments in an AGCM. ECHAM5, validate these results. In this paper, we proposed the air-sea interaction mechanism -'Ocean bridge'. It's very important to understand how the IOD modulates the precipitation anomalies in China in the following winter.In the latter part, the impact of Atlantic equatorial mode on the precipitation of China is studied. We derived a precipitation pattern from the regression analysis that shows wet anomalies over South China sea around equator and over northwest China(30°N), dry anomalies over southeast China and Indochina peninsula. Finally we draw a conclusion after all these analysis that maybe the tropical heating can influence the extratropical heating field, then excite the EC pattern leading to precipitation variations in China during summer.