影响延边东部气温预报失误的持续性低云过程分析

Analysis of sustained low cloud processes affecting temperature prediction errors in the eastern part of Yanbian

利用常规观测资料和ECMWF再分析资料,分析2022年12月23日夜间吉林省延边朝鲜族自治州最低气温预报失误的原因。结果显示:(1)降水结束后,虽然高空冷涡已完全移出,但中低层仍为东北风或北风,并没有西北干冷空气注入,导致中低层湿度较大,天空状况为阴或多云,不利于夜间地表长波辐射降温;(2)本次过程温度平流较弱,持续性低云和地面风对夜间气温几乎未下降起到关键性作用;(3)在近地面湿度未得到很好清除的背景下,配合弱上升运动、稳定大气层结的共同作用,使得低云维持;(4)在地形因素作用下,下沉增温利于延边东部气温升高,湿空气抬升达到饱和形成云,促使云体稳定维持在山前,同时也使延边东部风力增大,导致气温不易下降。

This article uses conventional observation data and ECMWF reanalysis data to analyze the reasons for the error in predicting the minimum temperature in Yanbian Korean Autonomous Prefecture,Jilin Province on the night of December 23,2022.It is found that after the end of precipitation,although the upper cold vortex has completely moved out,the middle and lower layers still have northeast or north winds,and there is no northwest dry and cold air injection,resulting in high humidity in the middle and lower layers and cloudy or cloudy sky conditions,Not conducive to nighttime surface longwave radiation cooling;The temperature advection during this process is weak,and sustained low clouds and surface winds have played a crucial role in almost no decrease in nighttime temperature;Under the background of not being well cleared of near ground humidity,combined with weak upward motion and stable atmospheric stratification,low clouds are maintained;Under the influence of terrain factors,sinking and warming are conducive to an increase in temperature in the eastern part of Yanbian.The rise of moist air reaches saturation and forms clouds,promoting the stable maintenance of cloud bodies in front of the mountains.At the same time,it also increases the wind power in the eastern part of Yanbian,making it difficult for the temperature to drop.