夏半年热带太平洋中部型海温异常与热带印度洋海盆模对同期中国东部降水的共同影响
投稿时间: 2016-01-18  最后修改时间: 2016-03-02  点此下载全文
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作者单位E-mail
王旭栋 南京信息工程大学大气科学学院 123484309@qq.com 
管兆勇 南京信息工程大学大气科学学院 guanzy@nuist.edu.cn 
周游 南京信息工程大学大气科学学院  
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目);公益性行业(气象)科研专项;灾害天气国家重点实验室开放课题
中文摘要:利用1961-2013年NCEP/NCAR再分析资料和HadISST月平均海表面温度(SST)资料,采用合成分析方法分析了夏半年热带太平洋中部型海温异常与热带印度洋海盆模(IOBM)的特征,并研究了不同位相配置时二者对同期中国东部气候的共同影响。结果表明:(1)太平洋中部型海温异常指数与印度洋海盆模指数统计学意义上独立。当热带太平洋中部型海温异常与IOBM同位相变化(记为PPNN事件)时,印太海温异常呈三极型分布;当热带太平洋中部型海温异常与IOBM反位相变化(记为PNNP事件)时,印太海温异常呈偶极型分布。(2)发生PPNN事件时,中国江淮流域水汽辐合,降水异常增多;发生PNNP事件时,中国长江及以南地区水汽辐散,降水异常偏少。(3)热带印太海温异常不同位相配置下影响中国东部降水的机制有所不同:发生PPNN事件时,水汽主要从海洋性大陆(MC)地区向长江与江淮流域输送;热带印太海温异常引起大气产生Gill型响应,维持中国东部的环流异常;低纬地区扰动通过经向三圈异常垂直环流引起长江与江淮流域降水异常增多。发生PNNP事件时,水汽未能从低纬地区直接辐散至长江流域;太平洋海温异常强迫导致的大气环流响应表现为环流中心位置明显西移,引起了长江及其以南地区水汽辐散,同时低纬地区对流层低层准定常Rossby波能传播也对长江流域扰动维持起一定的作用。这些结果对深刻认识中国东部地区夏半年降水异常成因和印度洋/太平洋海温异常不同分布的作用具有重要意义。
中文关键词:热带印度洋海盆模  太平洋中部型海温异常  中国东部降水  夏半年
 
Combined Influences of Tropical Central Pacific SSTA and Tropical Indian Ocean Basin Mode on East China Precipitation during Summer Half-year
Abstract:Based on the NCEP/NCAR reanalysis and HadISST monthly mean sea surface temperature(SST) data from 1961 to 2013, we have investigated the characteristics of tropical Central Pacific SST anomaly (SSTA) and Indian Ocean Basin Mode (IOBM) and their combined influences on rainfall variations over east China during summer half-year by composite analysis. Our results demonstrate that the tropical Central Pacific SSTA pattern index (CPI) and IOBM index (IOBMI) are almost independent of each other in sense of statistics. When the CPI and IOBMI are same signed, a tri-pole SSTA pattern is observed with colder (warmer) than normal SST over the Maritime Continent(MC) region along with warmer (colder) than normal SST in both equatorial Pacific and Indian Ocean (referred to PPNN cases). When CPI and IOBMI are oppositely signed, a dipole pattern of SSTA is found in tropical Indo-Pacific sector with warmer (colder) than normal SST in Pacific while colder (warmer) than normal SST in Indian Ocean (referred to PNNP cases). For PPNN cases, the precipitation is found to be more than normal and moisture converges over Yangtze-Huaihe River basin. For PNNP cases, the rainfall decreases significantly with strong anomalous divergence of water vapor in region south of the Yangtze River. Different mechanisms behind different anomalous rainfall patterns in east China are different for PPNN and PNNP cases. For PPNN cases, moisture mainly can be transported from MC to the Yangtze-Huaihe River basin. The anomalous circulations are generated and maintained due to Gill-type response of atmosphere to the tropical SSTA, especially the cooling over MC region. The anomalous vertical circulation cells over region from MC northward to Yangtze-Huaihe River show some connections between anomalous thermal forcing over MC and rainfall anomalies over Yangtze-Huaihe River basin. However, for PNNP cases, no moisture is anomalously transported into Yangtze River and its southern flank areas from MC region. Due to the significant westward shift of locations of SSTA center in Pacific, the centers of anomalous circulations at 850hPa are also shifted westward apparently as a Gill-type response of atmosphere to central Pacific SSTA pattern. As a result, the water vapor is explicitly transported from east China into central Pacific region. However, Rossby wave energy can propagate into region south of Yangtze River from MC region, facilitating the maintenance of anomalous anti-cyclonic circulation over region south of Yangtze River. These results are beneficial to us for better understanding the cases of rainfall anomalies and the role of SSTA patterns in Indo-Pacific sector in inducing precipitation anomalies in east China.
keywords:Tropical Indian Ocean Basin Mode  Central Pacific SSTA  precipitation in east China  summer half-year
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