摘要
基于1961—2010年中国西南地区26站春季月平均降水资料、NCEP/NCAR再分析资料和Hadley全球海表温度(SST)资料,分析了西南地区春季降水年际变化特征及其与海温异常(SSTA)的关系。利用全球大气环流模式ECHAM5进行降水异常对关键海域SSTA响应的敏感性试验。结果表明,西南春季降水年际变化特征十分明显,与同期赤道中太平洋海温有显著的负相关,与中纬度太平洋海温有显著的正相关。数值模式研究显示,当春季赤道中太平洋处于SSTA冷位相时,局地降水减少,其西北侧产生副热带反气旋和中纬度西太平洋地区的气旋式环流异常的响应,我国西南地区对流层低层的东北侧受西太平洋异常气旋环流西部的东-东北风影响。赤道西太平洋海洋大陆区域降水增加,其西北侧的气旋式环流异常,使孟加拉湾低槽增强,西南地区南侧的偏南气流加强了向西南地区的水汽输送,该异常暖湿气流与从东北侧进入西南地区的异常冷空气相交绥,使西南地区春季降水增多。在年际时间尺度上,中纬度太平洋SSTA对西南地区春季降水异常的直接影响不明显,这与中纬度太平洋SSTA受赤道中太平洋SSTA的影响有关,其自身可能是对赤道中太平洋SSTA引起的大气异常的一种反馈。
Based on the monthly mean rainfall data in 26 stations of Southwest China from 1961 to 2010 and NCEP/NCAR reanalysis data and Hadley global sea surface temperature (SST) data, the interannual variation of rainfall over the southwestern China during spring and its relationship with sea surface temperature anomaly (SSTA) are analyzed. Sensitivity tests are conducted for the response of anomalous precipitation to SSTA over the key oceanic domains by the global atmospheric circulation model ECHAMS. The results show that the interarmual variation of rainfall over the southwestern China in spring is very significant. There are robust negative (positive) correlation coefficients between anomalous precipitation and SSTA over the equatorial central Pacific (the mid-latitude Pacific) during spring. Numerical model studies have shown that the local rainfall is suppressed and a subtropical anticyclone circulation anomaly (cyclonic circulation anomaly) is produced over the northwest of the equatorial central Pacific (mid-latitude western Pacific) when the equatorial Pacific is in a cold SSTA phase in spring. Anomalous northerly winds appear in the northeastern part of the southwestern China in the lower troposphere. The rainfall increases over the marine continent of the western equatorial Pacific while a cyclonic circulation anomaly appears in the northwest of the western equatorial Pacific. The trough over the Bay of Bengal enhances the southerly flow in the south of the southwestern China. It also enhances the transport of moisture to the southwestern China. The warm moisture intersects with anomalous cold air over the northeast of the southwestern China, so the rainfall increases during spring. On the interannual time scales, the impact of mid-latitude Pacific SSTA on rainfall in the southwestern China in spring is not significant, because the mid-latitude Pacific SSTA is affected by the equatorial central Pacific SSTA, with the mid-latitude Pacific SSTA being a feedback to the circulation anomaly caused by the equatorial central Pacific SSTA.
出处
《热带气象学报》
CSCD
北大核心
2015年第1期11-20,共10页
Journal of Tropical Meteorology
基金
国家重点基础研究发展计划项目(2012CB955903)
江苏省高校自然科学研究重大项目(13KJA170002)共同资助