Abstract:

By using the ERA-Interim global reanalysis wind and specific humidity data from 1979 to 2012, the evolution characteristics of low-level water vapor are analyzed with the methods of variation rate analysis, Mann-Kendall test and analogy deviation analysis. And based on the wind field difference, the moisture abnormality is preliminarily discussed. Results showed that the annual lower-level water vapor increased in recent 30 years. In the Qinghai Plateau and arid desert region, water vapor happened abrupt change in 1996, while in 1991 for the monsoon region. Furthermore, westerly winds weaken and southerly winds increased significantly after abrupt change occurred. Through quantitative analysis of the impact of wind field change on water vapor, we found that meridional wind positively contributed to water vapor in the Qinghai Plateau region, except negative contribution in summer, and zonal wind showed negative contribution. The meridional and zonal contribution were 0.28 g·kg^-1 and -0.46 g·kg^-1 in the monsoon region, respectively. In arid desert region, wind's contribution appeared positive in winter and spring, while negative in summer and autumn. Based on the wind's climatic pattern differences in specific regions and typical months, we found that influence of low-level wind field change on the distribution of water vapor was much more different within a single region. However, the configuration of wind fields in adjacent areas in different backgrounds and wind interaction between different areas are the main reasons for the change of water vapor.

Key words: eastern part of Northwest China, low-level moisture, wind field, interaction