近60年来登陆华南热带气旋降水的气候变化特征及其成因

The climatic characteristics and causes of precipitation related to tropical cyclones landing in South China in recent 60 years

采用华南67个气象观测站逐日降水资料和NCEP/NCAR再分析风场、表面气压场、高度场、海表温度场资料以及上海台风所提供的热带气旋资料,分析了1960—2016年登陆华南热带气旋降水(TCP)的气候变化特征及其成因。结果表明:(1)华南区TCP存在显著的地域差异,沿海最大,往西往北递减,EOF展开TCP的距平场前3个模态特征向量的累积方差贡献达70.6%,其中第一模态整个区域表现为一致的偏多或偏少;(2)华南区TCP和TC频数年代际变化特征明显,1960—1995年TCP的平均值远远高于1996—2016年TCP的平均值,两者差值54.6 mm/站,两个时段年平均登陆TC频数相差1.4个;(3)1995年之后,西太平洋副高脊线明显西伸,南海北部的偏东气流减弱,不利热带气旋在这一带西行登陆华南,同时1995年之后整个华南总体的水汽通量辐合减小,三者的共同作用使得1995年之后华南地区TCP比1995之前TCP明显减少。

Based on the daily precipitation data of 67 weather observation stations in South China,the wind,surface pressure,altitude and sea surface temperature fields of the NCEP/NCAR reanalysis datasets and the tropical cyclone data obtained from Shanghai typhoon institute,the climatic characteristics of precipitation associated with tropical cyclone landing in South China from 1960 to 2016 as well as their causes are analyzed.The results show that the tropical cyclone precipitation(TCP)reveals significant regional differences in South China,which is the largest over the coastal area and decreases from the west to the north.The first three eigenvectors of the EOF modes explains 70.6%of the variation in the TCP anomaly data.The first mode represents a consistent weaker or heavier precipitation in the whole region.The TCP and tropical cyclone frequency shows significant interannual variability.The average TCP from 1960 to 1995 is much higher than that from 1996 to 2016 with a difference of 54.6 mm per station,while the difference of the frequency of landfall tropical cyclone is 1.4 on average between the two periods.Starting from 1995,the ridge line of the western Pacific subtropical high extends remarkably westward and the easterly flow in the northern South China Sea weakens,which is unfavorable for the westward landfall of tropical cyclones in South China.Meanwhile,the convergence of water vapor flux weakens over the whole region.Under the joint influence of those three conditions,the TCP in South China after 1995 is significantly less than that before 1995.