陕西夏季旱涝的主要环流特征

Analysis on Atmospheric Circulation Anomaly of Floods /Drought Summer in Shaanxi Province

利用1961—2008年NCEP／NCAR再分析资料以及陕西地面月降水资料，采用EOF分解、合成分析等方法，分析了陕西夏季旱涝的时空分布特征以及前期气候系统的异常信号特征。结果表明：陕西夏季多雨年乌拉尔山高压脊和鄂霍次克海高压偏强，贝加尔湖低槽偏深，西太平洋副热带高压偏强，西伸脊点偏西。并且前期冬季中高纬度中亚长波脊偏强偏西，西太平洋副热带高压偏强，印缅槽偏弱，700hPa西北地区东部至华北偏北风异常偏强，赤道东太平洋出现暖水位相，西风漂流区海温偏低，印度洋海温偏高，陕西夏季易多雨；而陕西夏季少雨年西太平洋副热带高压偏弱，西伸脊点偏东，陕西主要受中亚高脊前西北气流控制。前期冬季中高纬度欧洲西北部低槽偏强，中亚长波脊偏弱，西太平洋副热带高压偏弱，印缅槽偏强，700hPa西北地区东部至华北偏南风异常偏强，赤道东太平洋出现冷水位相，西风漂流区海温偏高，印度洋海温偏低，陕西夏季易少雨。

Based on NCEP/NCAR reanalysis data and monthly precipitation data in Shaanxi Province from 1961 to 2008, the spatial and temporal distribution characteristics of summer precipitation and the abnormal signal of early climate system characteristics were ana- lyzed by using EOF and composite analysis methods. Results show that when the Ural Mountain and the Okhotsk Sea high were stron- ger, the Baikal trough was deeper, and the west Pacific subtropical high strengthened and extended westward in summer, there would be flooding in summer of Shaanxi. Whereas, when Shaanxi was controlled by the northwest flow in front of the Central - Asian ridge, the west Pacific subtropical high was weaker and extended eastward, it would be drought in summer of Shaanxi. When the Central - A- sian ridge was stronger and extended westward, the west Pacific subtropical high strengthened, the India- Burma trough was weaker, and there were abnormal strong north wind in the eastern region of Northwest to the North China at the level of 700 hPa, SST in the middle east equatorial Pacific was higher and in west wind drift area was lower, SST in India ocean was higher in the preceding winter, there would be flooding in summer of Shaanxi. Whereas when the Northwestern Europe trough was stronger, the Central - Asian ridge was weaker, the west Pacific subtropical high was weaker, the India - Burma trough was stronger, there were abnormal strong south wind in the eastern region of Northwest to North China at the level of 700 hPa, SST in the middle east equatorial Pacific was lower and higher in west wind drift area, and SST in India ocean was lower in the preceding winter, there would be drought in summer of Shaanxi.