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内蒙古夏季降水与亚洲纬向环流的联系

董祝雷1白美兰1衣娜娜2   

  1. 1.内蒙古自治区气候中心,内蒙古呼和浩特010051;
    2. 内蒙古自治区气象科学研究所,内蒙古呼和浩特010051
  • 出版日期:2018-04-30 发布日期:2018-04-30
  • 作者简介:董祝雷(1989— ),男,硕士,助理工程师,从事气候变化与降水研究. E-mail:dongzhl@outlook.com。
  • 基金资助:

    内蒙古自治区科技计划项目(20130431)资助

Relation Between Summer Rainfall in Inner Mongolia and Asian Zonal Circulation

DONG Zhulei1, BAI Meilan1, YI Nana2   

  1. 1. Inner Mongolia Climate Centre, Hohhot 010051, China;
    2. Inner Mongolia Institute of Meteorogical Science, Hohhot 010051, China
  • Online:2018-04-30 Published:2018-04-30

摘要:

利用1980—2015年内蒙古地区116站逐月降水数据、NCEP/NCAR再分析资料及亚洲经、纬向环流指数资料等,分析内蒙古夏季降水与中高纬环流因子的关系。结果表明:近36 a内蒙古夏季降水呈显著减少趋势,且具有显著的年代际变化特征,在1999年发生显著突变。内蒙古夏季降水与亚洲纬向环流存在负相关关系,尤其是内蒙古东部显著相关。通过环流场合成分析发现,在亚洲纬向环流指数高(低)值年,500 hPa位势高度距平场上,欧亚上空呈现出“+、-、+”(“-、+、-”)的环流形势,使得乌拉尔山高压脊减弱(增强),贝加尔湖高空槽变浅(加深),南北冷暖空气交换减弱(增强);850 hPa风场上,亚洲纬向环流指数高(低)值年,中国北方地区上空受反气旋(气旋)性环流控制,对流活动较弱(强),而西太平洋上空为异常气旋(反气旋)性环流,同时副热带高压强度偏弱(强),位置偏南(北)、偏东(西),使得输送到内蒙古地区的水汽较少(多),造成内蒙古东部夏季降水偏少(多)。进一步分析发现,亚洲纬向环流指数高、低值年,200 hPa纬向风距平场呈现相反的分布形势,在高(低)值年,西风急流轴位置偏西(东),强度偏弱(强),不利于(利于)内蒙古东部夏季降水偏多。

关键词: 内蒙古, 夏季降水, 亚洲纬向环流指数, 西风急流

Abstract:

Based on the monthly precipitation data of 116 stations in Inner Mongolia, NCEP/NCAR reanalysis data, Asian zonal and meridional circulation indices from 1980 to 2015, the relation between summer rainfall in Inner Mongolia and circulation in middle and high latitude was analyzed. The results show that the summer rainfall in Inner Mongolia presented a decreasing trend during 1980-2015 as a whole, the decadal change of summer rainfall was significant, and the mutation happened in 1999. The summer rainfall in Inner Mongolia was negative related with the Asian zonal circulation index, especially in eastern part of Inner Mongolia. According to composite analysis, when the Asian zonal circulation index was higher, there were a deeper polar vortex and shallower trough over Europe and Lake Baikal and a weaker high-pressure ridge over the Ural Mountain on 500 hPa geopotential height anomaly field, which formed a ‘+, -, +’ Eurasian teleconnection pattern and resulted in less frequent exchange of cold and warm air. However, in lower years of Asian zonal circulation index, there were a shallower polar vortex and deeper trough over Europe and Lake Baikal and a stronger high-pressure ridge over the Ural Mountain, which formed a ‘-, +, -’ Eurasian teleconnection pattern and resulted in more frequent exchange of cold and warm air. Meanwhile, in high (low) years of Asian zonal circulation index, there was an anticyclonic (cyclonic) circulation over northern China, which weakened (enhanced) convective activities on 850 hPa wind field. At the same time, the western Pacific Subtropical High was weaker (stronger) and extended southward and eastward (northward and westward), which wasn’t (was) beneficial to vapor transpot to Inner Mongolia, and then the summer rainfall in eastern Inner Mongolia was less (more). Furthermore, the distribution patterns of zonal wind anomaly field on 200 hPa was opposite in strong and weak years of Asian zonal circulation. In the years of strong (weak) Asian zonal circulation, the intensity of westerly jet was weaker (stronger) and its location was westward (eastward), which wasn’t (was) conducive to more rainfall in summer in eastern Inner Mongolia.

Key words:  Inner Mongolia, summer rainfall, Asian zonal circulation index, westerly jet

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