东亚季风湿润区水分收支的气候特征

Climate Characteristics of Moisture Budget in Humid Region Affected by East Asian Monsoon

采用1958-2007年NCEP/NCAR月平均再分析资料,分别从水汽通量、水汽通量散度以及区域内降水量与蒸发量差计算东亚季风湿润区的水分收支,分析其差异特征,结果表明:用不同方法计算的水分收支距平年际变化的相关系数分别为0.91,0.71和0.81,误差ε百分率分别为17.4%,44.1%和44%,其中利用水汽通量和散度计算得到的季风湿润区水分收支结果很接近。总体上看,整个区域全年表现为水分收入,春季和夏季的水分收入贡献最大,秋季和冬季贡献较小。在水汽经向输送中,南边界为主要的水汽输入区。从水汽输送计算的水分收支垂直分布来看,多年平均气候态下整个区域除850 hPa存在水分支出外,其余各层均为水分收入,3种方法计算的水分收支在4个季节的年际变化明显。

Based on 1958—2007 NCEP/NCAR reanalysis data,the characteristics of moisture budget in humid region affected by East Asian Monsoon are calculated by moisture transport,moisture flux divergence and P—E methods.The correlation coefficients of climatological variability calculated by these methods are 0.91,0.71,0.81,and the percentage ofεare 17.4%,44.1%and 44%.The results calculated by moisture transport and moisture flux divergence methods are nearly the same.The results reveal net income of moisture budget thoughout the year especially in spring and summer,while in winter and autumn it＇s relatively weaker.Using moisture flux divergence and P-E methods,the absolute errors in summer are larger than in other seasons.In spring and summer,water transport and moisture flux divergence are both stronger than those in autumn and winter.For the meridional moisture transport,moisture enters this area mainly from south boundary.For the zonal moisture transport,moisture enters through west boundary and departs from east boundary all the year.Overall,the period of positive moisture budget is from February to October calculated by moisture transport method,and from February to September by the other two methods.Vertical distribution of moisture budget is calculated by moisture transport method and moisture flux divergence method.It shows that the anomaly transport between 800—500 hPa is positive during 1960s and early 1970s and negative after that.Below 800 hPa,the values manifest negative before 1960s, and then turn to positive.There is net income of moisture at the whole layer except for the 850 hPa.By moisture flux divergence method,the calculated moisture convergence is positive above 450 hPa,and negative below.The interannual moisture budget variability of four seasons is quite obvious.