中国西北空中可降水量的年内非均匀性特征

Intra-annual inhomogeneity characteristic of atmosphere precipitable water over the Northwest China

利用NCAR／NCEP资料，通过引进表征时间分配特征的参数集中度和集中期对西北上空大气可降水量年内非均匀性特征进行分析，结果表明：一致性异常分布是西北上空大气可降水量集中度和集中期的最主要的空间分布特征；西北地区上空大气可降水量集中度和集中期近45年来主要表现为2～4年、6～8年的高频振荡；西北上空大气可降水量集中度异常强弱年其水汽输送特征存在显著差异，在集中度异常强年，西北东南部西南季风水汽输送较常年偏强，其余区域西风带水汽输送较常年偏强，由于充足的水汽供应使得整个西北地区上空大气可降水量与常年相比偏多；反之亦然。

Using NCAR/NCEP reanalysis data on wind fields, specific humidity fields and surface pressure fields from 1954 to 2004, month by month atmosphere precipitable water was calculated in the Northwest China, then its intra-annual inhomogeneity was analyzed in terms of the concentration degree and concentration period. The results show that consistent anomalous spatial distribution of the atmosphere precipitable water concentration degree （qcd） and period （qcp） is main distribution characteristic in Northwest China, and its westerly belt region is the most anomaly region. It is proved that the atmosphere precipitable water concentration degree and period have 2 -4a and 6 -8a high-frequency fluctuation periods, at present its concentration degree is lean towards becoming strong and concentration period is lean towards moving ahead. It is found that atmosphere precipitable water has prominence difference in anomaly years of concentration degree, annual average atmosphere precipitable water is liable to be much more in anomaly strong years, and vice versa; but atmosphere precipitable water has not prominence difference in anomaly years of concentration period. Furthermore, it is also found that in anomaly strong years of atmosphere precipitable water concentration degree, southwest monsoon water vapor transportation is higher than that of average year in the southeast of the Northwest China, and in the other areas westerlies water vapor transportation is higher than that of average years ; because of plenitudinous water vapor provision, thus atmosphere precipitable water is more than that of average years in Northwest China, whereas in anomaly weak years of atmosphere precipitable water concentration degree, southwest monsoon water vapor transportation is lower than that of average years in the southeast of Northwest China, and the other areas westerlies water vapor transportation is lower than that of average years; because of exiguous water vapor provision, thus atmosphere precipitable is no more than that of average years in the Northwest China.