Preliminary Analysis Of The North China Summer Rainfall Anomaly Regularity And Its Causes

In order to study the anomaly pattern of summer rainfall in North China and the cause responsible for the anomaly, the climate characteristics of summer rainfall in North China and related circulation pattern, water vapor transport and outgoing long-wave radiation (OLR) were analyzed in detail in this paper. More attention was paid on studying the relationship between sea surface temperature anomaly (SSTA) over the north Pacific and summer precipitation anomaly in North China and an AGCM was utilized to confirm the affection of SSTA on the summer rainfall of the North China. The results are as follows.i. The summer rainfall anomaly of North China is closely related to Indian low, west Pacific subtropical high, westerly troughs and ridges in mid-latitude, south Asia high, subtropical monsoon circulation and cold air activity on the corresponding period, and similar circulation pattern also appears in the preceding spring. ii. Water vapor transport along with southeast monsoon in the south of west Pacific subtropical high and water vapor transport over south China peninsula both have great affection on the water vapor transport over the North China region, and the affection of water vapor transport over south china peninsula is more important.iii. The reverse distributions pattern of SSTA over the east Pacific region and west wind drift region not only occurs in the summer of severe drought and flood years of North China, but also in the preceding spring. This pattern of SSTA distribution is related to summer rainfall anomaly of North China by means of the tropical convection activity and general circulation in the middle and high latitude.iv. The results of numerical experiment are consistent with statistic analysis results. The SST anomaly of the equatorial eastern Pacific and west wind drift region both have influence on the general circulation and summer rainfall in North China, and the influence is nonlinear, which is not only manifested through the intensity change of anomaly of general circulation and summer rainfall in North China, but also through the spatial distribution pattern of the anomaly.