长江流域及其周围地区夏季持续旱涝的预报问题

The Forecasting Problem of Persistent Droughts and Floods in Summer over the Yangtze River Valleys and Adjacent Areas

长江流域及其南北大范围地区夏季持续性旱涝的形成，常常和其四周地区环流异常有关。这种异常包括冷暖空气的异常，海气和地气相互作用的异常及水汽输送等方面的异常。因此，做该地区夏季持续性旱涝预报时，不能只局限在考虑某个因素的作用上，而是应该综合考虑这些因素的相互作用和共同影响。预报时，首先进行“环流判别”：即考虑冬春欧洲乌拉尔地区环流特征、澳大利亚地区地面气压特征、孟加拉湾-中国南海水汽输送特征，赤道中太平洋海温特征及青藏高原感热输送特征，判定当年夏季是属于多雨还是少雨的年份。然后，进行“切变定位”：根据大气环流具有隔季相关的特点，应用冬季850hPa切变线的位置，把雨区大致位置确定下来。

The forming of persistent droughts and floods in summer over the Yangtze River valleys andadjecent areas is often related to the anomalies of atmospheric circulation voer surrounding regionns ofthis area.These anomalies include the anomalies of cold-warm air,the interactions of sea-air andland-air,and moisture transfer.In causing summer drought and flood forecast of this area, we shouldnot only consider the role of an individual factor, but consider entirely the interactions and common in-fluences of these factors. The prediction step is as follows. (1) Circulation identification. According tothe features of the circulation in Ural region, sensible heat transfer, over the Tibetan Plateau, sea watertemperature of the equatorial middle Pacific, pressure distribution in Australia and moisture transfer inBay of Bengal-South China Sea, drought summer or flood summer of this area can be decided. (2) De-termining the position by shear lines. Based on some property of winter-summer correlation of atmos-pheric circulation, summer main-rainy belt will be found by January-February shear lines at 850 hPa.