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基于小时降水资料的华西秋雨精细化特征分析

Fine-scale analysis of hourly precipitation of West China autumn precipitation

  • 摘要: 华西秋雨是中国秋季主要的气候现象之一,其影响范围涵盖陕西、四川、重庆、贵州等多省(市),主要特征表现为多绵绵细雨。利用2011—2020年GPM卫星小时降水资料,统计分析了华西秋雨的强度-频次分布、持续时间、日变化等特征,结果表明:(1) 根据强度—频次特征,华西秋雨区可分为四川盆地中东部、云贵高原东部、青藏高原东缘三个典型区域。四川盆地中东部降水频率、降水强度两者均高,云贵高原东部降水频率低、降水强度强,青藏高原东缘降水频率高、降水强度弱。(2) 从降水日峰值位相看,青藏高原东缘降水量日峰值出现在夜间22∶00 (北京时,下同),四川盆地中东部降水量日峰值出现在次日清晨06∶00,两个区域之间自西向东存在降水日峰值位相的滞后;在云贵高原东部,降水量日峰值自西向东从傍晚18:00滞后至次日午后16∶00;形成了北部、南部两种日峰值位相空间演变型。(3) 从不同持续时间降水事件的日变化特征看,随降水持续时间延长,青藏高原东缘降水日峰值出现时间逐渐延迟。四川盆地中东部和云贵高原东部降水均存在午后短时和清晨长持续性两种类型,其中四川盆地中东部的清晨长持续性降水对该地区总降水的贡献较云贵高原东部偏大。

     

    Abstract: The West China autumn precipitation (WCAP) is one of the most important climatic features in western regions of China (e.g. Shanxi, Sichuan, Chongqing, Guizhou), which is mainly characterized as continuous rain. Using the GPM precipitation data from 2011 to 2020, this study statistically analyzes the hourly characteristics of WCAP, including intensity-frequency distribution, duration, and diurnal variation. It is found that there are three key regions of WCAP: the central-eastern Sichuan Basin, the east of Yunnan-Guizhou Plateau, and the eastern periphery of the Tibetan Plateau. Further analysis of the detailed characteristics and differences of hourly precipitation between the three regions are as follows. (1) As regards the precipitation intensity-frequency distribution, both high precipitation frequency and strong precipitation intensity are found in the central-eastern Sichuan Basin, while a low precipitation frequency but strong precipitation in⁃ tensity in the east of Yunnan-Guizhou Plateau, with a high precipitation frequency but weak precipitation intensity in the east periphery of the Tibetan Plateau. (2) The diurnal peak phase of WCAP presents two spatial evolution patterns. The first one is located in the northern re⁃ gions, which shifts from the eastern periphery of the Tibetan Plateau peaking at 22∶00 BT to the central-eastern Sichuan Basin peaking at 06∶00 BT the next morning, showing a peak phase delay from west to east between these two regions. The second one is located in the east of the Yunnan-Guizhou Plateau, with the diurnal peak shifting from 18∶00 BT in the western part of this region to 16∶00 BT the next day in the eastern part. (3) From the perspective of the diurnal variation characteristics of precipitation events, with the increase in precipitation duration, the diurnal peak phase of precipitation in the eastern periphery of the Tibet Plateau shows a gradual delay signature. Two types of pre⁃ cipitation appear in both the central-eastern Sichuan Basin and the east of the Yunnan-Guizhou Plateau: afternoon short-duration precipita⁃ tion and morning long-duration precipitation. However, the morning long-duration precipitation in the central-eastern Sichuan Basin con⁃ tribute more to the total precipitation than that in the east of the Yunnan-Guizhou Plateau.

     

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