热带海温变化对云南初夏干湿转换季节雨量的影响

INFLUENCE OF SST VARIATIONS OF THE TROPICAL OCEAN ON RAINFALL DURING THE SEASON WHEN DRYNESS TURNS TO WETNESS IN EARLY SUMMER IN YUNNAN

关键词:  海温变化  初夏雨量  影响机制

Key words:  sea surface temperature (SST) variations  rainfall in early summer  impact mechanism

摘要:

通过相关分析、诊断分析以及数值模拟试验来研究热带海温异常对云南初夏干湿转换季节雨量变化的影响,研究表明前期热带海温异常对云南初夏干湿转换季节雨量有明显的影响,海温与雨量的显著相关区与Walker环流的上升下沉支相对应。提前的时间尺度越长,海温所提供的可预报信息越少;时间尺度越短,提供的可预报信息越大。诊断分析及数值模拟研究还表明在赤道中东太平洋的暖位相期,孟加拉湾地区的季风低压和初夏索马里附近的越赤道气流及印度洋西南季风减弱,反之则加强。海温变化通过海气相互作用影响到季风活动,从而对云南初夏干湿转换季节雨量产生影响。

Abstract:

Utilizing correlation analysis, diagnostic analysis and numerical simulation experiment, influence of sea surface temperature abnormality of two tropical oceans on rainfall during the season when dryness turns to wetness in early summer in Yunnan is studied. The results show that the preceding phase sea surface temperature anomaly has an obvious effect on the rainfall and the distinct correlation area between SST and rainfall is corresponding to the branches ascending and sinking of Walker circulation. The longer the time scale is, the less predictable information the oceans provide; the shorter time scale, the less predictable information. Diagnostic analysis and numerical simulation results also show that monsoon depression in the Bay of Bengal, cross-equatorial flow in Somali in early summer and southwest monsoon in India weaken during warm phase of equatorial central and eastern Pacific. Otherwise, they strengthen. Sea surface temperature variations affect monsoon activity through ocean-atmosphere interaction, then affect the rainfall.