近20 a塔城地区暖区暴雪环流分型及成因分析

Circulation classification and cause analysis of the warm-area blizzards in Tacheng area in recent 20 years

选用2000—2019年11月—次年3月塔城地区7个国家气象观测站逐日降水、温度、常规地面和高空观测资料、美国国家环境预报中心(NCEP)再分析资料,确定近20 a塔城地区暖区暴雪天气过程并进行分析。结果表明:(1)塔城地区暖区暴雪发生于塔额盆地的塔城站、裕民站和额敏站,塔城站出现频次最多;时间分布上,11月和12月出现暖区暴雪的频次最高,且主要集中在11月中旬—12月上旬,1月次之,2月最少。(2)塔城地区暖区暴雪分为3类:低槽前部型、横槽底部型和西北急流型,地面低压为西方和西北路径。低槽前部型是最典型的暖区暴雪形势,主要出现在11月—12月上旬,发生在西西伯利亚低槽前部锋区与南支中纬度短波槽汇合区,地面低压为西北路径;横槽底部型主要出现在11月—次年1月,发生在极锋锋区底部偏西气流和中纬度暖湿西南气流汇合的强锋区中,地面低压为西方路径;西北急流型主要出现在11—12月,发生在极锋锋区西北气流中,地面低压为西北路径。(3)500~300 hPa强西北或偏西急流、700 hPa偏西低空急流、850 hPa暖式切变的叠置区与暖区暴雪落区一致,低槽前部型和西北急流型为锋前暖区产生暴雪,横槽底部型为低压右前部暖锋锋生产生暴雪。(4)低槽前部型和横槽底部型的水汽均为偏西路径,来自地中海、阿拉伯海的水汽经里海、咸海增强后向暴雪区输送;西北急流型有偏西和西北2条水汽输送路径,来自高纬度巴伦支海的水汽与来自中低纬度里海、咸海、地中海、阿拉伯海的水汽在巴尔喀什湖附近汇合后向暴雪区输送,较强的水汽输送伴随低层明显的水汽辐合,强辐合中心位于850~700 hPa之间。

Select daily precipitation,temperature,conventional ground and upper-air observation data,the national center for environmental prediction reanalysis data collected from seven national meteorological observatories in the Tacheng area of Xinjiang,China,from November 2000 to March 2019 to determine the warm snowstorm weather process in the Tacheng area over the past 20 years.The analysis results show the following:(1)The warm-area blizzards in the Tacheng area occurred in Tacheng Station,Yumin Station,and Emin Station in the Tacheng-Emin Basin,and Tacheng Station had the most frequent occurrences;in terms of time distribution,the frequency of warm-area blizzards occurred in November and December and was primarily concentrated in mid-November to early December,followed by January and the least in February.(2)The blizzard in the warm area of Tacheng is divided into three types:low trough front type,horizontal trough bottom type,and northwest jet type.The surface low pressure is primarily in the west and northwest path.The low trough front type is the most typical warm-area blizzard situation,which primarily occurs from November to early December and occurs in the confluence area of the frontal area of the low trough in West Siberia and the mid-latitude short-wave trough of the southern branch;the surface low pressure has a northwest path.The horizontal trough bottom type occurs primarily from November to January of the following year and occurs in the strong frontal area in which the westward airflow at the bottom of the polar frontal area and the warm and humid southwesterly airflow at the mid-latitude converge;the surface low pressure follows a westward path.The northwest jet type primarily occurs from November to December.It occurs in the northwesterly airflow in the polar frontal area,and the surface low pressure has a northwest path.(3)The superimposed area of 500-300 hPa strong northwest or westward jet,700 hPa westward low-level jet,and 850 hPa warm shear is consistent with the blizzard fall area in the warm area.The low trough front type and the northwest jet type produce blizzards in the frontal warm area,and the horizontal trough bottom type produces blizzards in the low-pressure right warm front.(4)The water vapor in the low trough front type and the horizontal trough bottom type is in a westward path.The water vapor from the Mediterranean Sea and the Arabian Sea is improved by the Caspian Sea,Aral Sea,and then transported to the blizzard area.The northwest jet type has two water vapor types in the west and northwest.The water vapor from the high-latitude Barents Sea and the water vapor from the mid-and low-latitude Caspian Sea,Aral Sea,the Mediterranean Sea,and the Arabian Sea converge near Lake Balkhash and are transported to the blizzard area.The strong convergence center is located between 850 hPa and 700 hPa.