江淮入梅前后气象因子变化特征及预报着眼点探析

针对2010年江淮地区入梅日预报偏差情况,利用2010年6—7月高低空实况资料和NCEP再分析资料,分析了入梅前后湿度、经向风、地转西风急流的变化特征,并结合1985—2005年21 a历史平均状况和近几年的变化特征,分析了江淮地区入梅前后气象因子变化的规律性、普遍性,丰富了江淮地区入梅预报着眼点。研究发现:有些年份地转西风急流从30°N以南北跳到30~37.5°N区域,对江淮地区进入梅雨期有很好的预示作用,且其稳定维持,有利于江淮梅雨期降水的持续。70%湿度区北跳到30°N的时间及持续时间对江淮地区入梅日的预报和梅雨期长度有着较好的指示作用。在30~35°N区域内v850 hPa-v200 hPa风速差值的突然增大和江淮地区入梅有着较好对应关系。这为梅雨的预报提供了新的思路和方法。

Variation features of meteorological factors about onset of Jianghuai Meiyu and its forecasting focus

In order to examine the forecasting error of the onset of Jianghuai Meiyu, 2010, the variation features of humidity, meridional wind, geostrophic westerly jet stream at the high and low levels and NCEP reanalysis data from June to July in 2010 as well as 21-year average conditions during 1985-2005 and variations in recent years were studied to confirm the regularity and universality of variation features about meteorological factors before and after Jianghuai Meiyu, providing new approaches and focus for Meiyu forecasting in Jianghuai. The study found that during some years the jump of westerly jets from 30°N to 30-37.5°N is a significant starting signal of Meiyu in Jianghuai, and its stable maintenance helps sustain the rainfall of in Meiyu season. The time interval and persisting period for northward jump of 70% humidity region to 30°N are effective indexes for forecasting Meiyu onset and its length. In 30-35°N region, the sudden increase of wind differences (v_{850 hPa}-v_{200 hPa}) may correlate with the Meiyu onset in Jianghuai. These findings offer new ideas for Meiyu forecasting in Jianghuai.