马斯克林高压的变化及其与ENSO的关系

使用1948-1999年的NCEP／NCAR再分析月平均资料，根据气候平均高度场的演变特征，利用850hPa马斯克林高压的特征闭合等值线所包含的格点数定义了马高面积指数，通过分析马高面积指数揭示了马高的变化特征及其与ENSO的关系。结果表明：（1）马高虽然常年存在，但存在明显的季节变化，北半球夏季最强，冬季最弱，由冬到夏的突然增强过程主要在5～7月，由夏到冬的减弱过程主要在8～11月；（2）马高的面积变化在整个时段内存在16a左右的周期，在1965年前有8a左右的周期，在1967年后有3～5a的周期，特别是在1990年代以后3～5a的周期更显著；（3）在年代际时间尺度上，马高面积在1976年有一个明显的跃变，1976年之前马高偏弱，1976年之后马高增强；（4）马高变化与ENSO有明显的对应关系，当厄尔尼诺发生时，马高增强，反之减弱。马高与ENSO关系秋季最好，冬季次之，夏季最差。因此，ENSO是影响马高年际变化的一个重要因子。

THE VARIATION OF MASCARENE HIGH AND ITS RELATIONSHIP WITH ENSO

With the NCEP/NCAR monthly mean reanalysis data from 1948 to 1999,an area index is defined to describe Mascarene high(MH),based on the evolution characteristics of climatological geopotential height at 850 hPa. By calculating the index the features of the MH's variations on different time scales are examined.MH exists all the year round,but it has obvious seasonal variations,the strongest in boreal summer whereas the weakest in boreal winter.An abrupt intensification of MH from winter to summer occurs during May~July,while an opposite weakening from summer to winter occurs during August~November.The variations of the MH's area index have distinct oscillatory components: a 16-year period for the whole period of time,an 8 year period before 1965,and a 3~5 year period after 1967 which is especially significant since 1990s.On the interdecadal time scale,the MH's area index has a remarkable shift in around 1976,indicating that MH is much weaker before 1976 and stronger after it.The relationship between the MH's variation and ENSO is also investigated.It is shown that MH is intensified during an El Nino event,and vice versa.Such a relationship is the best in autumn.Therefore,ENSO is an important factor that can influence the interannual variation of MH.