利用淮河流域4省20：00-次日20：00逐日降水量资料，界定了1961-2006年淮河流域持续性强降水过程，并利用NCEP资料，应用合成分析方法对强降水过程和前期环流特征进行了研究。结果表明，从持续性强降水开始之前到强降水过程中乌拉尔山附近阻高减弱，贝加尔湖以北到鄂霍次克海附近的阻高偏强；西太平洋副热带高压在500hPa上表现为西伸北抬，但在850hPa上西伸明显，基本无北抬；南亚高压范围明显扩大，尤其是淮河流域以北地区200hPa高度明显增大，在中国东部到日本上空200hPa急流中心也有明显变化。850hPa西南急流的建立与西太平洋副热带高压的西伸有关，同时乌拉尔山附近高压减弱，冷空气南下，东西气压梯度增大也有利于西南急流的建立。%By analyzing the daily precipitation data from 20：000 BST to next 20：00 BST in Henan, Shandong, Anhui and Jiangsu provinces, the persistent and strong precipitation process （PSPP） over the Huaihe River valley from 1961 and 2006 is defined. Based on the NCEP data, the synthesis method is used to analyse the variation characteristics of atmospheric circulation during and before the PSPP. Results show that, before and during the PSPP, 1 ）The blocking high near the Ural Mountains becomes weaker, while the blocking high to the north of the Lake Baikal and near the Sea of Okhotsk becomes stronger; 2）The western Pacific subtropical high extends to the north and to the west at 500 hPa, whereas it shows obvious extension to the west and almost no extension to the north at 850 hPa;3 ）The scope of the South Asia high extends obviously. Especially, the height at 200 hPa over the north the Huaihe River valley increases dramatically, and the 200 hPa high level jet center over the East China-- Japan changes remarkably as well. The low level jet at 850 hPa is related to the westward extension of the western Pacific subtropical high. And the weakening of the high pressure near the Ural Mountains, the southward-moving of the cold air, and the increase of east-west atmospheric pressure gradient are all beneficial to the formation of the low level jet.
展开▼
