中国东部夏季主要降水型与高原春季热力因子间的关系

Correlations between major summer precipitation pattern in East China and spring thermodynamic factors over the Tibetan

采用中国地面气象观测站2 474个站的降水资料以及NCEP/NCAR再分析资料,利用经验正交函数展开、相关分析和小波分析等方法,探讨了中国东部夏季主要降水型与春季高原大气视热源之间的可能相关特征,并初步分析了前春高原大气加热对东部夏季降水异常分布的影响机制。降水EOF分析表明,中国东部夏季降水主要分为:华南—江淮型和长江中下游型;相关和周期分析表明,300 hPa和400 hPa高原南部地区、500 hPa高原北部地区视热源与华南—江淮降水型之间相关显著,3个区域视热源均与华南降水呈负相关,且与江淮降水呈正相关;200 hPa高原偏北地区、500 hPa高原东部地区视热源与长江中下游地区降水呈负相关,而500 hPa高原西部地区视热源则与长江中下游降水呈正相关关系。以上春季高原不同高度关键区域的视热源可为预报夏季降水提供重要判据;从视热源与各个降水中心的相关特征可见,春季高原上空视热源加热场结构会影响中国东部夏季雨带南北位置的分布情况。由春至夏高原加热的"气泵"作用,使得由孟加拉湾和南海地区水汽输送经高原东部地区后,折向东输送至中国大陆东部地区。加热偏强时,水汽向北输送分量加强,雨带偏北,降水"南少北多",反之亦然。

Based on the precipitation data from 2474 weather stations and NCEP/NCAR reanalysis datasets,the possible correlation characteristics between the major summer precipitation pattern in East China and the spring apparent heat sources over Tibetan are investigated with Empirical Orthogohal Function （EOF）,correlation and Morlet wavelet analysis method,in addition,the influencing mechanism of the apparent heat source （Q1） on the distribution of summer precipitation anomaly is preliminarily analyzed.The results of EOF analysis show that two major precipitation patterns exist in eastern China：South China-Jianghuai and Middle-lower Yangtze River pattern; results of correlation and period analysis show that Q1 of the southern Tibetan at 300 hPa,400 hPa and northern Tibetan at 500 hPa have significant relations with the South China-Jianghuai precipitation pattern,which are all negative with South China precipitation but positive with Jianghuai precipitation; Q1 of the northern Tibetan at 200 hPa and eastern Tibetan at 500 hPa have negative relation with the middle-lower Yangtze River precipitation pattern,while for summer western Tibetan at 500 hPa,it is positive.Q1 areas discussed above can provide significant basis for summer precipitation forecast in eastern China.Summary from the relevant characteristics between Q1 and summer precipitation centers shows that Q1 in spring over Tibetan can affect the location distribution of summer rain belts in eastern China.The heat-pump effects of the Tibetan from spring to summer lead to the water vapor transport from the southeastern Tibetan to the eastern China.When the heating is strong,the strengthening northern transportation-component of water vapor creats‘ North wetSouth dry＇ pattern; in the contrary,the weak transportation of water vapor to the north tends to provide ‘North dry-South wet＇ pattern.