基于再分析资料,系统分析了1979—2018年中亚干旱区大气水汽含量、水汽收支、降水量、实际蒸发量等水分循环要素的时空变化特征。结果表明：（1） 中亚水分循环要素空间差异明显,降水量和实际蒸发量在天山和帕米尔等山区及周边绿洲区为高值区,荒漠平原地区为低值区,而大气水汽含量相反。（2） 1979—2018年中亚水汽含量呈微弱的减少趋势,变化速率区域差异明显,咸海周边区域明显减少,而新疆大部和天山山区明显增加;中亚地区水汽输送以纬向输送为主,经向输送相对较弱,不同区域水汽收支和变化有较大差异,其中西边界和北边界水汽输送减少,东边界和南边界水汽输送增加;水汽收支在中亚西北部、中亚南部、帕米尔高原和天山山区呈增加趋势,而中亚北部和新疆大部有减少趋势。（3） 与水汽输送变化的表现不同,1979—2018年中亚降水量有增加趋势,为4.14 mm·（10a）^-1,且年际波动较大,显著增加趋势分布在中亚北部、新疆大部和天山山区,而在中亚西北部和南部有明显减少趋势。（4） 中亚实际蒸发量有微弱的增加趋势,在中亚北部、天山山区和帕米尔高原有明显增加,而在里咸海、中亚南部和新疆南部干旱地区明显减少。从季节来看,各水分循环要素季节变化与年变化时空分布特征基本一致。研究成果有助于进一步了解中亚干旱区大气水分循环演变及机理。

The arid regions of Central Asia, which are “upstream” of China in terms of their influence on weather and climate, are characterized by a general shortage of water resources and the fragility of ecosystems. The atmospheric water cycle is the key link in the transformation of water resources and ecosystems in this region. In this study, we reassessed the temporal and spatial variation of water cycle elements, such as atmospheric water vapor content, water vapor budget, precipitation, and actual evaporation, in the arid region and subregions of Central Asia, from 1979 to 2018. The results of our analysis show clear spatial differences in the water cycle elements of Central Asia. Precipitation and actual evaporation are high in mountainous areas, such as Tianshan Mountains and Pamir and surrounding oasis areas, and low in the desert plain areas, whereas atmospheric water vapor content shows an opposite pattern. In terms of temporal changes, from 1979 to 2018, the water vapor content in Central Asia showed a weak decreasing trend, with obvious regional differences in the rate of change. Water vapor content in the surrounding areas of the Aral Sea decreased significantly, whereas in most of the areas of the Xinjiang and Tianshan Mountains, it increased significantly. Zonal transport is the main mode of water vapor transport in Central Asia, compared with the relatively weak meridional transport. Large differences were found in the water vapor budget over different regions; the water vapor transport tended to decrease in the western and northern boundaries and increased in the eastern and southern boundaries. Water vapor revenue and expenditure showed an increasing trend in northwestern Central Asia, southern Central Asia, the Pamir Plateau, and the Tianshan Mountains and a decreasing trend in northern Central Asia and most of Xinjiang. In contrast to the change in water vapor transport, the precipitation in Central Asia increased from 1979 to 2018, with an increase of 4.14 mm·(10a)^-1 and a large interannual fluctuation. The significant increasing trend of precipitation is distributed in northern Central Asia and most of the Xinjiang and Tianshan Mountains, whereas there was a significant decreasing trend in northwestern and southern Central Asia. The actual evaporation in Central Asia showed a slight increasing trend, increasing significantly in the northern part of Central Asia, the Tianshan Mountains, and Pamir but decreasing significantly in the Caspian Sea area, Aral Sea, southern Central Asia, and southern Xinjiang. In terms of seasonal variation, the temporal and spatial distribution of seasonal and annual variations of water cycle elements was generally consistent. The results of our analysis contribute to a better understanding of the evolution and mechanism of the atmospheric water cycle in the arid regions of Central Asia.