中国西北地区夏季降水的气候特征

利用西北地区119个气象站1961-2000年夏季降水资料,分析其空间分布特征和时间变化规律.选择典型多雨与少雨年,对美国NCEP/NCAR高空流、地气系统射出的长波辐射(OLR)场、赤道北太平洋海温(SST)与西北夏季降水的关系进行对比分析.结果表明:西北地区夏季降水具有明显的空间差异,最少的是新疆的吐鲁番气象站,为6.7 mm,最多的是陕西的佛坪气象站,为446.9 mm.多雨年北半球500 hPa极涡明显浅,西太平洋副热带高压强,700 hPa矢量风距平场中国西北地区为辐合区,700 hPa比湿距平中心位于中国西北地区,OLR主要负距平中心在西北地区,SST负距平主要在赤道太平洋东部.少雨年500 hPa极涡深,西太平洋副热带高压很弱,700 hPa矢量风距平场中国西北地区为辐散区,700 hPa比湿距正中心位于孟加拉湾西部,OLR主要正距平中心在西北地区;SST正距平主要在赤道太平洋东部.

Climatic Characteristics of Summer Precipitation in Northwestern China

This paper analyzes the spatial distribution and temporal change of summer precipitation in northwestern China based on the data of summer precipitation measured by 119 meteorological stations in northwestern China during the period of 1961-2000, and compares the relationships between the summer precipitation and the American upper-air circulation at NCEP/NCAR 500 hPa, OLR field, vector wind at 700 hPa, humidity field and SST in the typical years with high and low precipitation. The results show that there is a significant spatial difference in summer precipitation in northwestern China, the minimum summer precipitation (6.7 mm) occurred at Turpan Meteorological Station in Xinjiang, and the maximum one (446.9 mm) occurred at Foping Meteorological Station. The very eddy at 500 hPa over the Northern Hemisphere is obvious and shallow, the west Pacific subtropic high is strong, there is a convergence of anomaly field of summer vector wind at 700 hPa over northwestern China, the main negative anomaly center of summer OLR is also over northwestern China, and the negative anomaly of SST is mainly over the east equatorial Pacific Ocean. The very eddy at 500 hPa in low-precipitation years is deep, the west Pacific subtropic high is very weak, there is a divergence of anomaly field of summer vector wind at 700 hPa over northwestern China, the center of summer specific humidity anomaly at 700 hPa is over the west Bengalese Gulf, the positive anomaly center of summer OLR is mainly over northwestern China, and the positive anomaly center of SST is manly over the east equatorial Pacific Ocean.