2007—2020年威海机场4-9月平流低云的变化特征及影响因子分析

Characteristics and impact factors of advection low clouds in Weihai airport from April to September during 2007—2020

分析了威海机场2007—2020年(2014年资料缺失)4—9月平流低云的年际和逐月变化特征,揭示有利于平流低云出现的月尺度大气环流场及其可能的影响因素。结果表明:威海机场年均出现39.8个平流低云日,多年平均的平流低云日数从4月开始逐月增加,7月达到最多,为11.5 d,8—9月又逐渐减少,呈单峰结构。平流低云出现时常伴有轻雾和平流雾,两者出现频率合计达79.4%;西南风是平流低云出现时的主风向,180°~220°内的风向占比达50.0%。威海机场位于地面稳定的东高西低天气形势下,有利于平流低云的出现,此时山东半岛南部海域的海表温度较低,其上有明显暖平流,上暖下冷的结构有利于大气层结稳定,大气向海洋放热而降温,易使气流在山东半岛南侧登陆时形成低云并维持。年际尺度上黑潮的强弱对威海机场平流低云日数的多寡有较好的指示意义。

This paper analyzes the interannual and monthly variation characteristics of advection low clouds from April to September during 2007 to 2020(lack of data in 2014)at Weihai airport,and reveals the atmospheric circulation conducive to the emergence of advection low clouds and its possible influencing factors.The results show that:There are 39.8 advection low cloud days in Weihai airport every year.The climatological number of advection low cloud days increases from April to July,and gradually decreases from August to September,showing a single peak structure.Advection low clouds appear accompanied by light fog and advection fog,with a total frequency of 79.4%.The southwest wind is the main wind direction when advection low clouds appear,and the wind direction in the range of 180°~220°accounts for 50.0%.Under the influence of a stable synoptic situation of high pressure in the East and low pressure in the west,the area of Weihai airport is conducive to the emergence of advection low clouds.At this time,the sea surface temperature in the southern sea area of Shandong Peninsula is relatively low,and there is an obvious warm advection on it.The structure of warm air up and cold air down is conducive to the stability of the atmosphere.The atmosphere releases heat to the ocean and cools down,which is easy to form low clouds and maintain when the air landing on the southern side of Shandong Peninsula.The strength of the Kuroshio on the interannual scale is a good indication of the number of advection low cloud days of Weihai airport.