1981-2010年中国西北地区东部大气可降水量的时空变化特征

利用1981-2010年NCEP/NCAR再分析资料以及同期西北地区东部58个气象站的日降水、蒸发资料,采用一种新的方法统计分析了该地区大气可降水量的时空分布特征,并对大气可降水量与实际降水量的相关性进行了分析。结果表明:西北地区东部大气可降水量空间分布极不均匀,无论年或季,均呈现为西北少东南多的分布特征。逐月大气可降水量分布呈单峰型,7月最大,1月最小; 近30年,西北地区东部年、各季大气可降水总量均呈微弱减少趋势,四季中夏季减少趋势最为显著,冬季不明显; 58个站点30年平均的实际降水量空间分布与大气可降水量分布基本一致,年际变化也呈微弱减少趋势; 大气可降水总量与实际降水量呈显著正相关,年平均相关系数为0.545,各季节中春季相关系数最大,秋季和冬季次之,夏季最小; 不同区域大气可降水总量与实际降水量的相关性因季节不同而不同,总体来说,甘肃东部、南部和陕西中部、南部相关性较高,大气可降水量对降水量的贡献较大; 将大气可降水量和降水日数结合起来,更能准确、客观地反映一段时间内总的大气可降水量分布情况。

Spatial and Temporal Changes of Atmospheric Precipitable Water in the Eastern Part of Northwest China from 1981 to 2010

Based on the NCEP/NCAR reanalysis data and daily precipitation and evaporation data at 58 meteorological stations from 1981 to 2010, authors adopt a new method to analyze the spatial and temporal distributions of atmospheric precipitable water in the east part of northwest China. In addition, the correlation of atmospheric precipitable water and precipitation are also analyzed. The results show that the atmospheric precipitable water is unevenly distributed in the east part of northwest China both for annual total and in four seasons, which is gradually decreasing from southeast to northwest. Besides, the precipitable water present a slight decreasing trend in the east part of northwest China and the reducing rate is different from season to season in the recent 30 years. The precipitation distribution is similar to the atmospheric precipitable wate. It also showed a trend of weak reduction in the studied area. In addition, the actual precipitation is significantly and positively related with the atmospheric precipitable water, and the correlation coefficient is maximum in spring and minimum in summer. The correlation of precitpitation and the atmospheric precipitable water in different regions is rather complex, for it changes along with the season. In general, the correlation is higher in the east and south Gansu and the central and south Shaanxi. It would be more accurate and truthful to combine the atmospheric precipitable water with the rainy days to assess precipitable water.