珠江口雾过程数值模拟及生消概念模型建立

NUMERICAL SIMULATION AND CONCEPTUAL MODEL ESTABLISHMENT OF FOGS OVER PEARL RIVER ESTUARY,CHINA

利用深圳市气象局1953—2013年的气象观测资料对该地区出现的雾日（包括能见度达到10km及以下的轻雾和能见度达到1km及以下的雾）特征进行统计分析。结果表明,该区域的轻雾日与雾日多发于冬春季节的02时和08时,发生时地面10m平均风速为1.9m/s,近60年来总雾日有增多趋势;能见度达到1km以下的雾日多发于冬春季节的08时,发生时地面10m平均风速为1.0m/s,近60年来有减少的趋势。利用NCAR/NCEP再分析资料统计得出珠江口地区出现雾日的典型地面天气形势可分为均压场型、冷高压底部型和冷高压后部型三种;850hPa天气形势可分为一般均压型、弱高压脊附近均压型和弱低槽、低涡附近均压型三种。在统计分析的基础上,利用中尺度气象模式WRF对三种典型地面天气形势下的珠江口雾日个例进行数值模拟研究。结果表明：WRF模式能较好地再现珠江口雾的形成、维持与消散过程。880hPa附近逆温层的演变、960-920hPa水汽输送的变化与近地面风场的特征是影响珠江口地区雾生消过程的三个重要因素。结合多年统计分析结果、中尺度模式模拟结果以及珠江口地理环境和气候特征,建立了珠江口雾生消过程的概念模型。

Meteorological observations of 1953-2013 from Shenzhen Meteorology Bureau were used to analyze the characteristics of mists （visibility lower than 10 km） and fog （visibility lower than 1 km） days. It was found that in the past 60 years there is an increased trend for mists and a decreased trend for fogs. The mists mainly occurred at 2 a.m. and 8 a.m. in winter and spring and the average wind speed at 10m above ground was 1.9 m/s, while fogs mainly occurred just at 8a. m. with wind speed of 1.0 m/s. NCAR/NCEP reanalysis data were utilized to determine the weather patterns of fog days over Pearl River Estuary （PRE）. They can be divided into three types ： a uniform pressure field, bottom of a cold high-pressure, rear portion of a surface cold high-pres- sure and also three types at 850 hPa： a uniform pressure field, uniform pressure near a weak ridge, uniform pressure near a trough, respectively. Based on the results of statistical analysis, the mesoscale meteorological model WRF was used to simulate three typical types of fog episodes over PRE. The results showed that the WRF model captured the formation, maintenance and dissipation processes of fogs over PRE fairly well. The three main factors influencing the development of fogs over PRE were the evolution of temperature inversion layer near 880 hPa, the transportation of water vapor at 960 - 920 hPa and the moderate wind field near the ground. Combining the results of statistical analysis, ver PRE, we concluded with conceptual numerical simulations, geographic environment and climate features o- models of fogs＇ formation and dissipation.