Analysis and numerical simulation of the teleconne ction between Indian summer monsoon and precipitation in North China

In the early 1980s, Chinese meteorologists discovered the positive correlation in summer rainfall between India and North China and the correlation was confirmed by some researches at home and abroad. Based on a variety of meteorological data from 1951 to 2005 and numerical simulations, the present study investigates such a correlation between Indian summer monsoon (ISM) and precipitation in North China. Furthermore, we discuss the intrinsic relations of the positive (northwest India) negative (the Tibetan Plateau)positive precipitation anomaly (North China) teleconnection pattern from two aspects of thermal and dynamical factors, which not only confirms the precipitation teleconnection previously discovered again, but also reveals the influence mechanism of the ISM on the rainfall in North China. The results show that: (1) when the ISM is strong (weak), the precipitation in North China tends to be more (less) than normal; however, when the rainfall in North China is more (less) than normal, the probability of the strengthening (weakening) of the ISM is relatively lower. This implies that the ISM anomaly has more impact on the rainfall in North China. (2) The Indian low usually dominantly impacts on the intensity of the ISM. When the Indian low deepens, the low troughs in midhigh latitudes are also frequently strengthened, and the ridge of the western Pacific subtropical high (WPSH) extends westwards. The southwesterly water vapor transport originated from low-latitudes and the southeasterly water vapor transport along the southwestern flank of the WPSH converge in North China, which is favorable for more rainfall there than normal, and vice versa. (3) The simulation results by using of the regional climate model developed by National Climate Center (ReGCM_NCC) also capture the salient feature of the precipitation teleconnection between India and North China. The simulated anomalous atmospheric circulations are approximately the same as diagnosed ones, which confirms the existence and reliability of such a teleconnection from another angle.