2000~2017年江淮地区持续性异常降水低频特征分析

Low-Frequency Characteristics of Persistent Abnormal Precipitation over the Jianghuai Region during 2000-2017

利用中国气象局提供的2000~2017年地面气象观测站点逐日降水资料、NCEP逐日4次FNL再分析资料和NOAA向外长波辐射(OLR)资料,依据持续性异常降水指数挑选出67个低频降水事件,之后采用功率谱分析、Lanczos滤波、位相合成分析等统计方法,对江淮地区低频降水的统计特征和高中低层的低频环流场特征进行了分析。结果表明:江淮地区的异常降水事件降水最强的阶段平均持续3~8天,降水带分布在长江沿岸及其以南地区,中心主要位于安徽南部和江西北部。低层(850 hPa),江淮地区的持续性异常降水受到西北太平洋上空西北向传播的低频信号和河套地区东南向传播的低频信号共同作用的影响;中层(500 hPa),江淮地区的持续性异常降水主要受到位于其上空的气旋式系统和南海–菲律宾海地区的反气旋系统的影响;高层(200 hPa),南海–菲律宾海的反气旋环流、江淮地区西北侧的气旋环流及巴尔喀什湖的反气旋环流,三者构成西北–东南向移动的低频波列,与江淮地区持续性异常降水的活跃中断相对应。

Using the daily rain data gauge observations at stations provided by the China Meteorological Ad-ministration, NCEP FNL reanalysis data and outgoing longwave radiation (OLR) data provided by NOAA, 67 low-frequency rainfall events are selected from eighteen summers based on the persistent abnormal precipitation index, then, using statistical methods such as power spectrum analysis, Lanczos filtering and phase synthesis analysis to analyze the low-frequency characteristics of persistent abnormal rainfall processes over the Jianghuai region during 2000-2017. The results show that the precipitation period of the persistent abnormal precipitation events over the Jianghuai region lasted 3 - 8 days on average, and the rain-belt was distributed along the Yangtze River and its south, and the center was mainly located in southern of Anhui and northwestern of Jiangxi. At the lower level (850 hPa), the persistent abnormal precipitation over the Jianghuai region is affected by the low-frequency signals transmitted from the northwest Pacific and the low-frequency signals transmitted from the Hetao region;in the middle level (500 hPa), the persistent abnormal precipi-tation over the Jianghuai region is mainly affected by the cyclonic system above it and the anticyclone system in the South China Sea-Philippines;in the upper level (200 hPa), the anticyclonic circulations of the South China Sea-Philippines and Barkash Lake, the cyclone circulation on the northwest side of the Jianghuai region, constitute the low-frequency wave train moving northwest-southeast, and corresponding to the active interruption of persistent abnormal precipitation over the Jianghuai region.