2019年沈阳一次凌晨气温骤升过程成因精细分析

2019年12月2日01时沈阳国家基本气象站(沈阳站)气温1 h内异常回升了6.5℃,利用常规和加密地面观测站实况、NCEP再分析及沈阳站逐小时风廓线雷达资料,从系统配置、热力学诊断、城市热岛效应等方面对此次异常升温事件成因进行精细分析。结果表明:沈阳站异常升温阶段,超低空到近地面暖脊过境造成辽宁大部分地区出现气温回升,暖脊过境是引发沈阳站午夜时分异常升温的原因之一;沈阳站位于沈阳市的东南部,当地面风为西北风时,风从温度相对较高的城区吹向郊区,造成沈阳南部郊区各站气温回升,与北部郊区对比得出升温幅度约为3—4℃。城市热岛中心向下风方漂移是沈阳站气温骤升又一原因。值得注意的是,气温回升前的温度基础值对气温回升幅度存在一定程度影响,回升前的基础温度越低,则回升后造成的升温幅度越大。

Fine analysis of causes of an early-morning abnormal temperature rise in Shenyang in 2019

Air temperature observed at a national weather station in Shenyang increased by 6.5℃ in an hour at 01:00 on December 2, 2019.We accurately analyzed the causes of this abnormal temperature-increase process from the aspects of system configuration, thermodynamic diagnosis, and urban heat island effect, using regular and encrypted observation data, National Centers for Environment Prediction (NCEP) reanalysis data, and wind profiler radar data in Shenyang.The results indicated that a warm ridge between extremely low altitudes and near the surface passes by during the abnormal temperature-increase period, which is the major reason for the increase of air temperature at the midnight over most regions of Liaoning province.The national weather station is located in the southeastern region of Shenyang.In the presence of the northwesterly surface winds, air flows move from warm urban regions to cold suburb regions in Shenyang.This results in the increase in air temperature observed at all weather stations in the southern part of Shenyang, increasing by 3-4℃ in comparison with stations in northern suburbs.Therefore, the urban heat island center moving to the leeward is another reason for the abnormal temperature-increase event.Moreover, the base value of air temperature before temperature rise can affect the temperature-increase degree.The lower the basic temperature is, the greater the temperature-increase degree is.