南海北部近岸春季海雾的年际变化

Inter-annual variability of spring sea fog over northern South China Sea

利用ICOADS(International Comprehensive Ocean-Atmosphere Data Set)资料对南海北部春季海雾的年际变化特征进行研究。春季南海北部的海雾多集中在近岸海区,远离岸线的海区海雾较少发生。南海北部近岸春季海雾日数偏多年份有4个(1969、1983、1986、1987年);雾日数偏少年份有5个(1971、1999—2002年)。利用NCEP/NCAR月平均再分析资料,对海雾日数偏多、偏少年份的850hPa等压面上各要素分别进行合成分析。850hPa等压面上,华南沿海上空常年存在一个由南向北的暖平流。南海上空的空气湿度较大,在海雾日数偏多年份大气湿度减小,偏少年份湿度增大。南海上空850—1 000hPa等压面之间存在一股来自西太平洋的水汽输送。在海雾日数偏多年份水汽输送增强,海雾日数偏少年份水汽输送减弱。

The inter-annual characteristics of spring sea fog over the northern South China Sea were investigated by using the ICOADS （International Comprehensive Ocean-Atmosphere Data Set） data. Sea fog occurred more frequently in the nearshore area than in the outer sea area. There were more sea fog days in the four years including 1969, 1983, 1986 and 1987 and less fog days in 1971 and from 1999 to 2002. NCEP/NCAR data was used to analyze the geopotential height and air temperature at the pressure level of 850hPa. It is shown that there existed a warm current along coastal South China in spring. The specific humidity at 2m height above the sea was generally large over the South China Sea, but it decreased in the foggy years and increased in the less foggy years. A vapor transport from the western Pacific Ocean to the South China Sea existed between 1000hPa and 850hPa, which increased in the foggy years and decreased in the less foggy years.