新疆北部小时降雪特征及大暴雪天气影响系统研究

新疆北部是我国降雪高频区之一,随着全球变暖降雪量呈显著增加趋势,对新疆气候产生重要影响,由于观测资料限制对该区域小时降雪研究还未开展,影响降雪精细化预报和服务能力提升。因此,利用新疆天山山区及其以北（以下称“新疆北部”）2012年11月—2021年2月50个国家气象站小时降雪观测资料,分析了冷季（11月—翌年2月）小时降雪特征,并按日降雪量从高到低挑选30个大暴雪过程分析其小时降雪特征、影响系统及典型环流配置。结果表明：（1） 阿勒泰北部、塔城盆地、伊犁河谷为降雪小时数（SHN）高频区,可达200 h·a^-1以上;天山山区SHN高频区为海拔1800~2000 m的中山带,达127.3 h·a^-1,2000 m以上降雪很少。（2） 北疆和天山山区小时降雪量（R）≤1.0 mm·h^-1量级SHN占比分别为91.7%和91.9%,对降雪量贡献分别为70.7%和68.9%,R>1.0 mm·h^-1为小时极端降雪事件,对北疆和天山山区降雪量贡献分别为29.3%和31.1%。（3） 极端暴雪过程平均SHN为25.5 h,平均降雪量为30.7 mm,雪强约为1.2 mm·h^-1,大暴雪过程由长时间降雪导致,降雪持续时间是开展大暴雪研究和进行预报服务的关键点,造成大暴雪过程的影响系统主要有中亚长波槽、中亚低涡、乌拉尔山长波槽和西西伯利亚低涡（槽）,占比分别为30.0%、6.7%、13.3%和50.0%,中纬度长波槽（涡）和北方西西伯利亚低涡（槽）系统各为50.0%。

Hourly snowfall characteristics and influence system of heavy snowstorm in northern Xinjiang

Northern Xinjiang has been identified as one of China’s snowiest regions. Snowfall has significantly increased as a result of global warming, having a substantial impact on the climate in Xinjiang. Due to the limitation of observation data, no research on hourly snowfall has been conducted in this area, affecting the improvement of snowfall fine forecasting and service ability. The hourly snowfall characteristics in the cold season (November to February next year) are analyzed using data from 50 national meteorological stations in the Tianshan Mountains area of Xinjiang and its north (northern Xinjiang) from November 2012 to February 2021. Thirty heavy snowstorm processes are selected according to their snowfall amount and the daily snowfall amount for analysis of their hourly snowfall characteristics, impact systems, and typical circulation configuration. The results show the following: (1) Northern Altay Prefecture, the Tacheng Basin, and the Ili River Valley have a high snowfall hourly number (SHN), which can exceed 200 h·a^-1. Tianshan Mountains’ high-frequency area is the middle mountain belt, with an altitude of 1800-2000 m, and the SHN is 127.3 h·a^-1. There is little snow above 2000 m. (2) In northern Xinjiang and the Tianshan Mountains, the proportion of SHN in the order of R≤1.0 mm·h^-1 is 91.7% and 91.9%, respectively, and its contribution to snowfall is 70.7% and 68.9% respectively. R>1.0 mm·h^-1 is an hourly extreme snowfall event, yet it contributes 29.3% and 31.1% of the snowfall in the northern Xinjiang and Tianshan Mountains, respectively. (3) The average SHN and snowfall of the heavy snowfall process are 25.5 h and 30.7 mm, respectively, with a snowfall intensity of 1.2 mm·h^-1. Heavy snowfall processes are caused by prolonged snowfall, and snowfall duration is key for heavy snowfall process research, forecasting, and service. Among the Central Asia trough systems, the Central Asia vortex, the Ural Mountain trough, and the West Siberian vortex (trough) system account for 30.0%, 6.7%, 13.3%, and 50.0%, respectively, while the middle latitude long wave trough (vortex) and West Siberian vortex (trough) systems account for 50.0%.