华北地区热带气旋降水量的气候诊断

Climatic diagnosis of tropical cyclone precipitation over North China

利用1950～2002年热带气旋降水量资料,对华北地区由热带气旋引起的降水进行了分析.结果表明,华北地区热带气旋降水量的空间分布很不均匀,平均山东半岛东部最大,向西具有减少的趋势,这种趋势与热带气旋降水频数相一致,地形的影响使降水量的空间分布复杂化.对于热带气旋过程降水量的大小,地形的影响更为重要,从河北东部经西部到河南南部沿着燕山南麓和太行山东麓分布着大的过程降水中心,此外,受热带气旋影响的最西站点随年代向东偏移.热带气旋降水量季节变化表现为8月最大,10月最小;年际变化明显,具有显著的2～3年振荡周期;年代际变化表现为20世纪50,60和70年代相差很小,80年代后具有明显减少的趋势.各区域热带气旋降水量的年际和年代际变化显示,华北西部的山西和北部的内蒙减少的趋势最强.

The precipitation over North China caused by tropical cyclone （TC） was analyzed with the TC precipitation data during 1950-2002. The results show that the spatial distribution of TC precipitation is severely uneven and the highest TC precipitation occurs in the east of Shandong Peninsula with a decrease trend from east to west. This trend is consistent with TC precipitation frequency. The terrain is also an influencing factor, which makes the spatial distribution of TC precipitation much complicated. For the quantity of the precipitation, the terrain is more important. Some heavy precipitation centers lie along the south foot of the Yan Mountain and the east of the Taihang Mountain from the east of Hebei Province towards its west areas and the south of Henan Province. Meanwhile, the west observation station under the impact of TC precipitation moves from west to east. The seasonal change of TC precipitation is that the maximal value occurs in August and the minimal value occurs in October; the inter-annual change of TC precipitation is evident with an oscillation period of 2-3 years, with a little variation occurring in the 1950s, the 1960s, and the 1970s and a decrease trend obviously occurring in the 1980s. The inter-annual and inter-decade variations of TC precipitation in different regions show that the decrease trends of Shanxi Province （in the west of North China） and Neimenggu （in the north of North China） are the most notable.