西安地区高温天气分月精细化预报指标

Monthly Fine Forecast Indexes of High Temperature Weather in Xi'an Area

利用1987—2016年西安城区和6个区县的高温天气资料,运用天气学原理和统计学方法,分析≥35℃、≥37℃和≥40℃高温天气的时空分布特征。研究表明近30 a西安地区高温日数整体表现为增加趋势,≥35℃、≥37℃和≥40℃高温日线性倾向率分别为3.3、3.0和0.2 d·(10 a)-1;≥35℃和≥37℃高温日7月出现最多,≥40℃高温日6月出现最多。根据500 h Pa大气环流形势,将西安地区高温天气分为西北气流型、西太平洋副热带高压型(以下简称副高)(细分为副高影响型和副高控制型)以及大陆暖高型3种类型。通过分析高温发生前一天08:00的高低空暖空气温度范围和位置分布、地面气压场分布、24 h变压强度、气温和云量、ECWMF数值模式850 h Pa温度和海平面气压场预报结果以及5个指标站08:00 850 h Pa和地面温度等因子,细化总结出6—8月逐月≥35℃、≥37℃和≥40℃高温精细化预报指标。

Based on high temperature weather observation data in Xi'an urban and six counties from 1987 to 2016,the spatial and temporal features of high temperature weather with temperature above 35 ℃,37 ℃ and 40 ℃ occurring in Xi'an area were analyzed by using synoptic principle and statistical method. It showed that high temperature days increased in recent 30 years,concretely speaking,for temperature above 35 ℃,37 ℃ and 40 ℃,the increasing rate of high temperature days were 3. 3 days per 10 years,3 days per 10 years and 0. 2 day per 10 years,respectively. As for monthly variation,high temperature days with temperature above 35 ℃ and 37 ℃were most in July,while high temperature days with temperature above 40 ℃ were most in June. According to different atmospheric circulation on 500 h Pa,the circulations influencing high temperature weather in Xi'an were classified into 3 types,including northwest airstream type,subtropical anticyclone type( subtropical anticyclone impact type and subtropical anticyclone control type) and continental warm anticyclone type. Furthermore,the monthly fine forecast indexes of high temperature weather with temperature above 35℃,37 ℃ and 40 ℃ were summarized by analyzing the position and temperature range of warm air in upper and lower level,sea-level pressure,the 24 h surface allobaric field,temperature and cloud cover,EC numerical weather prediction product and temperature on850 h Pa and surface in five reference stations,etc,these forecast factors all occurred at 08: 00 BST on the previous day of high temperature.