山东夏季空中水汽分布和水汽输送特征

利用山东省气象站的降水量资料和JRA-55、NCEP/NCAR再分析资料,分析了1962-2016年山东夏季整层大气可降水量、降水转化率、水汽通量及输送路径的分布特征和变化规律,探讨了夏季降水与水汽通量及其散度的相关性和多雨年的水汽来源。结果表明:从常年值来看,山东平均夏季降水量为401.2 mm,大气可降水量为3478.8 mm,降水转化率为11.5%。降水转化率和降水量的时空演变特征更加一致,经向水汽输送和局地水汽通量散度与地面有效降水的关系更加密切,当大气可降水量充沛、外部水汽输送充足并出现局地水汽辐合时,更加有利于山东南部地区降水的发生发展,从而形成夏季降水量和降水转化率气候特征表现出东南地区大于西北地区的空间分布型态。西北太平洋、南海、孟加拉湾和鄂霍茨克海至日本海是造成山东夏季降水异常偏多的重要水汽源地,巴尔喀什湖至贝加尔湖地区是重要的冷空气输送区域;当山东上游盛行偏西风时,自新疆和青藏高原至内蒙古的狭长带出现异常水汽扰动并发展,是由水汽异常引起的水汽通量异常对山东局地降水异常贡献的主要条件。

Characteristics of Atmospheric Water Vapor Distribution and Transport during Summer over Shandong Province

Based on monthly rain-gauge precipitation data and JRA-55,NCEP/NCAR reanalysis data,the climatology distributional and variational characteristics of whole atmospheric column precipitable water,precipitation conversion efficiency,water vapor flux and transport during summertime from 1962 to 2016 in Shandong Province were investigated;The correlativity between summer precipitation and both moisture fluxes and divergences,as well as the water vapor sources in above normal rainfall years,were discussed. Results indicate that:As for the climatology,averaged precipitation,precipitable water,and precipitation conversion efficiency are401. 2 mm,3478. 8 mm and 11. 5%,respectively. The spatial-temporal evolutions exhibit more consistent for precipitation and precipitation conversion efficiency compared with that of summer rainfall and whole atmospheric column precipitable water,which are even opposite in some specific years or periods. The surface effective precipitation tends to be more influenced by meridional water vapor transport and regional moisture flux divergences. When the atmospheric precipitable water and water vapor transport are abundant,the regional moisture convergence is more favorable for the occurrence and development of precipitation in the southern part of Shandong,thus make the special climatology of both rainfall and precipitation conversion efficiency distribute as more rainfall in the southeast Shandong than that in the northwestern part. By comparison,the main source of water vapor in rainy years is transported from the Northwest Pacific by the easterly and southerly of the western North Pacific subtropical high,lead to strong convergence in the southeastern Shandong;While in the heavy rainy years,water vapor in the tropical Pacific and the Indian Ocean also transported by both tropical and middlehigh latitude general circulation systems,the Philippine Anticyclone,cross-equatorial flow and westerly of an anticlockwise moisture flux center located in Outer Mongolia for instance,thus give rise to intensive convergence in the west and south part of Shandong. The Northwest Pacific,South China Sea,Bay of Bengal,and Okhotsk to Japan Sea are significant water vapor sources which could bring about more summer rainfall in Shandong. Besides,the essential cold-air activity area extends from Balkhash Lake to Baikal. When the upstream region of Shandong prevails westerly wind,an anomalous water vapor disturbance appeared and developed in a belt area from Xinjiang and the Qinghai-Xizang Plateau to Inner Mongolia is the main factor for precipitation anomaly arising from anomalous moisture transported by mean circulation.