内蒙古地区多年大气可降水量及其转化效率研究

Study on Atmospheric Precipitable Water and Precipitation Conversion Efficiency of Muti-Year in Inner Mongolia

利用1961-2015年NCEP/NCAR再分析资料和内蒙古119个国家站月降水资料,对大气可降水量、水循环次数、水汽通量及其散度的时空分布特征进行分析。结果表明:(1)内蒙古地区四季平均大气可降水量均值为8~14 mm,自南向北、自东向西递减,65年的年际变化上总体呈减少趋势,受锋区活动及大气环流季节突变影响,4月、6月分别出现了2次突然增长,10-11月出现1次突然减少;(2)水循环次数夏季最高,春、秋季次之,冬季最低,呈自东北向西南递减,年际变化呈增加趋势,受纬度影响量值及变率均明显不同;(3)内蒙古地区水汽输送以偏西风为主,但夏季偏南风输送的加强直接导致大气可降水量及水循环次数的增加;(4)各季水汽输入量均小于水汽输出量,导致内蒙古地区长期处于水汽收支失衡状态;(5)水汽通量散度的空间分布即水汽的辐合辐散与水循环次数的空间分布较为一致,说明水循环次数能够客观反映大气可降水量的转化情况。

The spatial and temporal distributions of atmospheric precipitable water and precipitation conversion efficiency in Inner Mongolia region were analised by using the NCEP/NCAR reanalysis data and monthly precipi- tation data of 119 stations from 1961 to 2015. The results show that： （ 1 ） The average of atmospheric precipitable water in Inner Mongolia region is 8 - 14 mm. The atmospheric precipitable water is gradually decreasing from south to north and from east to west. The interannual variation showed a decreasing trend in recent 65 years. In- fluenced by front activities and the abrupt change of atmospheric circulation, there were two times of sudden growth in April and June, and one time of sudden reduction from October to November. （2） The number of wa- ter cycle in Inner Mongolia region is the highest in summer, the second in spring or autumn, and the lowest in winter, which is decreasing from northeast to southwest, and the interannual variation shows an increasing trend. （3） The main path of water transportation in Inner Mongolia region is westerly, but the southerly transportation directly lead to the increase of precipitation and water cycle. （4） Seasonal water vapor input is less than the out- put, which leads to an imbalance of water vapor in Inner Mongolia region. （5） The spatial distribution of water vapor flux divergence is consistent with the spatial distribution of water cycle, indicating that the number of water cycles can objectively reflect the transformation of precipitable water vapor.