Subjects: Geosciences >> Geography submitted time 2022-12-14 Cooperative journals: 《干旱区研究》
Abstract：
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.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2022-08-08 Cooperative journals: 《干旱区地理》
Abstract：基于19792019年欧洲中期数值预报中心（ECMWF）的ERA-Interim逐月再分析数据和英国东安格利亚大学气候研究中心（CRU）的陆面逐月降水数据，分析夏季北非副热带高压（北非副高）与中亚夏季降水的关系。结果表明：北非副高的脊线指数和东伸脊点指数变化与中亚夏季降水联系紧密。在2个指数的单独变化和协同变化下，中亚夏季降水和大尺度环流异常分布存在很大不同。副高脊线主要导致中亚夏季降水南北反相变化，副高东伸脊点位置对中亚中南部降水存在重要影响。当副高位置偏东偏北时，里海和咸海上空受异常气旋控制，哈萨克斯坦大部分地区降水偏多，新疆受蒙古异常反气旋控制，降水偏少；当副高位置偏西偏南时，中亚地区主要受异常反气旋控制，其东北部存在异常气旋切变，对应中亚东北部降水偏多，其余区域降水偏少；当副高位置偏西偏北时，中亚上空受异常反气旋控制，大部分地区降水偏少；当副高位置东偏南时，中亚上空受异常气旋控制，热带印度洋水汽通过两步输送的方式，进入中亚上空，形成有利的动力和水汽条件，导致中亚大部分地区夏季降水偏多。
Subjects: Geosciences >> Atmospheric Sciences submitted time 2022-01-21 Cooperative journals: 《干旱区地理》
Abstract：天山山区是新疆干旱区降水最为充沛的区域，已有针对该区域降水的研究大多使用日降水及以上尺度资料，降水日变化特征分析相对较少。基于天山山区11个国家气象站20122018年夏季（68月）逐小时降水资料，分析降水特征量（包括降水量、降水频次和降水强度）的日变化特征，揭示降水与海拔高度的关系。结果表明：总降水量和总降水频次的峰值出现在20:0022:00，谷值出现在12:0013:00。夜间降水多于白天，主要由长时降水贡献。总降水强度呈现出白天整体增强、夜间偏弱的特征。降水与海拔高度密切联系，小雨等级降水在高海拔山区频发，在海拔2000 m左右存在一个最大降水带。
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