南亚高压的时空演变特征及其对西南地区降水的影响

Spatial and Temporal Evolution Characteristics of South Asian High and Its Impact on Precipitation in Southwest China

摘要: 本文根据1979~2017年全国地面站点的降水观测资料和同期全球水平空间分辨率为0.75˚ × 0.75˚的ERA-Interim位势高度高空观测逐月再分析资料，通过计算南亚高压的面积指数、强度指数和比较东脊点、主中心位置，研究了其时空演变特征及对我国西南地区降水的影响。结果表明：1) 南亚高压存在明显的季节演变，4月各指数增大，7月达最强，9月开始减弱，表明南亚高压夏季最强，冬季最弱，南亚高压夏季存在，冬季消失。2) 南亚高压夏季最强是在6月第3候发展到最强，延伸到青藏高原上空并在高原持续活动；10月第3、4、5候，南亚高压开始减弱，逐渐从高原撤离。3) 南亚高压各指数之间相互影响，特别是面积指数和东脊点有非常好的一致性，同增同减，近年来南亚高压呈现出增大的趋势，具体表现在面积指数和强度指数近年一直增大，东脊点位置向北、向东移动。4) 南亚高压强度异常与我国西南地区的降水密切相关。南亚高压强年，西南地区降水普遍偏多，南亚高压弱年，西南地区降水减少，因此南亚高压强度和西南地区的降水呈明显正相关。

Abstract: This paper analyzes the precipitation observation data from national ground stations from 1979 to 2017 and the ERA-Interim sounding observation with global spatial resolution of 0.75˚ × 0.75˚ contemporarily. By calculating the area index and intensity index of the South Asian high and comparing the relative location of the east ridge point and the main center position of the South Asian high, we studied its characteristics of spatiotemporal changes and its impact on precipitation in south-western China. The results show that: 1) There is an obvious seasonal evolution in South Asia high. The indices start to increase in April, become strongest in July and finally weaken in September. This phenomenon indicates that the South Asian high is strongest in summer and weakest in winter, appears in summer and disappears in winter. 2) In the third Hou of June, this period is the strongest of the South Asian high of summer which extends to the Qinghai-Tibet Plateau and continues to be active on the plateau; in the third, fourth and fifth Hou of October, the South Asian high begins to weaken and gradually withdraw from the plateau. 3) The indices of South Asia high interact be-tween each other, especially the area index and the east ridge point which have a very good consistency, with the same increasing and decreasing trend. In recent years, the South Asian high has shown an increasing trend, which is manifested by area index and intensity index in recent years and the east ridge point moving northward and eastward. 4) The intensity anomaly of the South Asian high is closely related to precipitation in southwestern China. In the strong years of South Asia, the precipitation in the southwestern China is generally high whereas in the weak years of the South Asian high the precipitation in the southwestern China is reduced. Therefore, the intensity of the South Asian high is significantly positively correlated with the precipitation in the southwestern China.