关键词: 西北干旱区, 降水, 水汽输送, 蒸发, 水汽辐合

Abstract:

With global temperature increasing, climate in arid areas also has a marked change. Based on NCEP reanalysis datasets, the characteristics and changes of meridional and zonal water vapor transportation, evaporation, water vapor convergence and divergence in the arid areas (35°N- 50°N, 73°E-105°E) of northwest China during 1961-2010 were analyzed, at the same time, their relationships with rainfall were also discussed. Conclusions are as follows:(1) The meridional vapor transportation was net input in winter, spring and autumn over the arid area of northwest China, whereas the zonal vapor transportation was net output, the total vapor transportation was also net input. In summer, both the meridional and zonal transportation were net outputs. Precipitation in the northwest arid area increased in each season during 1961-2010, and the increasing trend was significant in winter and spring, but it was not obvious in summer and autumn. The decrease of zonal water vapor net output in winter resulted in an increase of total water vapor transport. While the decrease of zonal water vapor net input in spring and autumn as well as the increase of zonal water vapor net output in summer caused the reduction of total water vapor input in spring, summer and autumn. (3) The evaporation increased significantly in each season in the northwest arid areas, and the increasing rate was the biggest in summer. (4) The water vapor flux divergence decreased significantly in each season, which meant the convergence of water vapor became stronger, especially in summer. (5) Considering the effect of water vapor transport, evaporation and water vapor convergence, the increase of evaporation and water vapor convergence was the main positive driving force to precipitation in northwest arid area, but external vapor transportation could also affect precipitation there.

Key words: northwest arid area of China, precipitation, water vapor transport, evaporation, vapor convergence