2016年1月梅州降水异常偏多的成因分析

Analysis of the Causation of Anomalously More Precipitation in Meizhou in January 2016

利用1960—2016年逐年1月份的NCEP再分析资料,以及气候指数资料对梅州2016年1月份的降水异常偏多的原因进行分析。结果表明:当月500 h Pa高度场上,欧亚中高纬度为两槽一脊,乌拉尔山脊偏强,有利于冷空气的堆积,北亚高纬地区横槽转竖引导冷空气大举南下,同时西太副高偏强,有利于副高西北侧西南暖湿气流向梅州输送,南北冷暖气流的交汇给梅州带来了明显降水天气;200 h Pa距平风场上,梅州上空处于气旋式距平风场东南部的辐散区域,有利于高层的抽吸作用,而低层偏强的西南风给梅州带来了充沛的水汽;水汽通量大值区以及水汽通量散度负值中心出现的时间与强降水时间吻合;海温场上赤道中东太平洋海域为大范围的正值区,是典型的El Ni1o年,为当月降水偏多的发生提供了有利的气候背景。

Using the NCEP reanalysis data of the Januaries from 1960 to 2016 and climatic indexes,we examined the causes for anomalously more precipitation in Meizhou in January 2016. The result is shown as follows. On the 500 hPa geopotential height field of the month,two troughs and a ridge were present in the mid-and higher-latitudes of the Eurasian continent with a relatively strong high ridge in the Ural Mountains,which was favorable for cold air mass to accumulate. A traverse trough in the high latitudes of North Asia became meridional to induce cold air to progress southward. In the meantime,a subtropical high was relatively strong over the western Pacific,which was conducive for a warm and humid air stream on the northwest side of the subtropical high to transport to Meizhou so that the interaction between cold and warm air flow brought significant precipitation to the region. On the anomalous wind field at 200 hPa,Meizhou was in a diverging area in the southeast of a cyclonic anomalous wind field,favorable for upper-level sucking effect. In the meantime,strong low-level southwesterly brought sufficient amount of water vapor to the region. The timing of the occurrence of the maximum zone of water vapor flux and the center of negative divergence for water vapor flux was consistent with that of intense rainfall. An extensive zone of positive sea surface temperature existed over the equatorial eastern and central Pacific,characteristic of a typical El Ni1 o year,which was favorable for anomalously more rain to occur in January 2016.