中国西北东部地区春季降水及其水汽输送特征
CHARACTERISTICS OF PRECIPITATION AND WATER VAPOR TRANSPORT DURING SPRINGTIME IN THE EASTERN NORTHWEST CHINA
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摘要: 文中使用1962~2002年逐日降水资料和NCEP/NCAR再分析资料,考察了中国西北东部地区春季降水及其水汽输送的气候特征和异常变化。分析表明,该地区春季降水时段集中、变率较大,具有明显的年际和年代际变化特征;水汽主要来源于南部季风区,输送路径集中于青藏高原和偏南方向,偏东方向输送相对较弱,而且西太平洋副高和高原对输送路径具有显著影响;多雨年的异常水汽输送主要来源于偏东方向海洋上的异常向西输送和前期由菲律宾及其北部海区的向北输送;对异常水汽通量进行分解后发现:由环流异常引起的平均水汽输送在多数年份的降水正异常过程中起主导作用,而平均环流对异常水汽的前期输送对于局地降水异常也有一定贡献;多雨年的环流异常集中表现为高度场上位于中国东北地区的正异常中心,这有利于偏东、偏南的异常水汽输送到西北东部。结果初步认为西北东部地区的空中水汽资源具有一定的补偿能力和利用潜力,该地区是维系西北内陆地区空中水资源乃至水分循环过程的水汽输送关键区。Abstract: The basic anomalous charact eristics of the precipitation and water vapor transport during springtime in the eastern Northwest China (ENWC) were investigated by using daily precipitation data from NMC and NCEP/NCAR reanalysis data from 1962 to 2002. The analysed results show that, with the significant interannual and interdecadal variability features, the spring time precipitation in ENWC is comparatively concentrative and the water vapor is mostly from the southern monsoon region via three basic approaches including the Qinghai-Tibet Plateau, south, and east directions. Also, the anomalous water vapor is recognized by the west ward transportation from eastern sea area, and the previous northward transport from the Philippines and its neighboring ocean. Furthermore, through decomposition of anomalous water vapor transport find that the averaged water vapor transport induced by general circulation anomaly plays an leading role in most positive precipitation anomaly years and the anomalous water vapor transported previously by the basic general circulation is important to local rainfall. The farther analysis shows that a positive anomaly center of general circulation in height fieldlying in the region of Northeast China helps to the east erly and southerly water vapor transport anomalies in rainy years. At the Rametiine, its also found that air water resource in ENWC has certain petential of compensation and utility, and ENWC is a key region of water vapor transport which keeps air water resource and water cycle process in Northwest China.