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

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 of ε are 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.