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青藏高原地区地表热力异常与夏季东亚环流和江淮降水的关系

ISSN号：0577-6619
期刊名称：《气象学报》
时间：0
分类：P456.7[天文地球—大气科学及气象学]
作者机构：[1]南京大学大气科学系,南京210093, [2]中国气象局乌鲁木齐沙漠气象研究所,乌鲁木齐830002
相关基金：“国家重点基础研究发展计划”（973）项目：“我国南方致洪暴雨监测与预测的理论和方法研究”（2004CB418300）和国家自然科学基金面上项目“我国温度和降水气候极端事件及其与全球不均匀增暖的联系”（40675042）.

关键词：青藏高原地区, 温度梯度, 空间热力差异, 夏季东亚环流, 江淮流域降水, Tibetan Plateau and its circumjacent areas, Temperature gradient, Spatial thermal contrast, Summer circulation in East Asia, Rainfall in the Jianghuai area

中文摘要：

利用NCEP/NCAR再分析月平均资料和中国160个站降水资料,以及由国家气候中心提供的西太平洋副高脊线指数资料,分析了青藏高原地区多年平均地表温度季节转换（3—6月）的空间特征,结合均方差分析,确定高原主体（28°—38°N,75°—100°E）、高原东部以北区域（38°—48°N,90°—105°E）和高原西部以北区域（38°—45°N,75°—90°E）为关键区,分析了1951—2002年5月不同关键区地表温度的空间变化与夏季东亚季风环流和江淮降水的关系。结果发现,这3个区域地表温度异常均对夏季东亚850hPa环流有显著的影响。5月高原和其以北区域地表温度异常存在较大尺度的热力对比,由此,将高原主体和其以北区域的温度异常之差定义为一个指数,反映这种热力差异。相关分析发现：当5月这一热力差异增大（减小）时,夏季东亚中高纬的中高层（500—200hPa平均）西风加强（减弱）,且西风中心轴线位置南移（北抬）;造成西太平洋副热带高压脊线位置偏南（偏北）,致使夏季东亚季风环流偏弱（偏强）,江淮流域降水增多（减少）。

英文摘要：

The relationship between the surface thermal anomalies （STA） over the Tibetan Plateau （TP） and the summer rainfall over the Yangtze and Huaihe River （Jianghuai） areas, has been studied by many researchers. However, most previous studies focused on the temporal variation of STA, and less attention was paid to the correlation between the spatial variation of STA over TP and the Jianghuai summer rainfall. The present paper aims to explore this correlation. By use of the NCEP/NCAR Reanalysis monthly mean data, the precipitation data at 160 stations in China, and the index data of the Western Pacific subtropical high ridgeline （WPSHR） provided by the National Climate Center of China, the spatial features of the mean surface temperature over the TP and its circumjacent areas during the seasonal transition （March to June） are analyzed. By mean square deviation analyses, three areas are selected：1） the TP main area（28° - 38°N,75° - 100°E）, 2） the area to the northeast of the TP（38° - 48°N,90° - 105°E）, and 3） the area to the northwest of the TP（38°-45°N,75°-90°E）. The relationship between the spatial variation of STA over the three areas in May and the summer circulation over East Asia and rainfall over the Jianghuai areas from 1951--2002 is further investigated. The results show that the STA over the three areas are evidently related to the 850 hPa summer circulation. A large-scale thermal contrast exists between the TP and the area to its north in May, and an index is defined to reflect the intensity of the large-scale thermal contrast. When the thermal contrast enhances （weakens）, the south-north gradient of the mean air temperature in the mid-upper troposphere （500--200 hPa） enhances （weakens）, too. This results in the speeding up （slowing down） of the westerly winds in the mid-upper troposphere and their shifting to further south （north）. The WPSHR also shifts to further south （north） than normal. So the East Asian summer monsoon weakens ?

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