广东“回南天”现象分析及其预报

Analysis and Forecasting of High-Humidity Weather in Guangdong in February and March

利用室内地板温度、气温、露点、湿度,以及NCEP 1°×1°分析数据等资料,对2012年广东2—3月冬春过渡季节"回南天"(高湿天气)的5次个例的天气形势、气象要素特征和物理变化过程进行了分析。结果表明:冷空气影响结束后,广东上空迅速转受暖湿空气控制,当室外空气露点高于室内物体温度时"回南天"现象就会产生;"回南天"是出现在冷暖急转的天气背景下的;冬春季节当持续控制广东的冷高压脊快速减弱,同时925hPa上有明显的偏南气流时,预报员就要考虑是否会出现"回南天"现象;气温快速回升,露点高于室内物体温度是"回南天"出现的必要条件,要重点分析未来露点的变化;"回南天"有两种结束方式,即冷性结束和暖性结束。

During the transition season between winter and spring in Guangdong Province,many objects such as indoor floors,walls and glasses easily become damp and are often covered by a thin clay of condensed water.An analysis is made of such five cases of the special high-humidity weather during February and March in 2012in the aspects of physical processes and circulation patterns,air temperature and humidity characteristics,etc.The results indicates：after the termination of the influence of cold air, warm and wet air affects Guangdong when the dew point of outdoor air is higher than the indoor object temperature,and a high-humidity weather event appears on the background of cold air making a sudden turn into warm air.During the transition season between winter and spring,when the high pressure ridge weakens rapidly,meanwhile there is obvious southerly air flow on 925hPa,it is necessary to consider whether there appears a high-humidity phenomenon during daily weather forecasting;the rapid rise of air temperature is the necessary condition for the high-humidity phenomenon;the trend of future dew point should be selectively analyzed.The high-humidity phenomenon normally disappears in two ways：cold ending and warm ending.Namely,Guangdong is affected by new cold air and the air temperature and dew point decrease dramatically,and the dew point is lower than the indoor object temperature;or air temperature rises up and lasts for a certain time period and the indoor object temperature is higher than the outdoor air dew point.