南海北部台风引起的广西近岸增减水研究

A Research on Fluctuations of Water Level in Guangxi Coast Caused by Typhoons in the Northern South China Sea

引起广西近岸增减水主要是台风导致的风暴潮所致。受台风影响,北海站42年中最大增水1.45m,最大减水-1.87m。受台风走向影响,广西近海总是先减水后增水。引起广西近海增减水除去台风直接作用外,还有广东沿海陆架波西传的间接作用。西传的陆架波一部分直接穿过琼州海峡进入北部湾,另一部分绕过海南岛以顺时针方式进入北部湾。2001年7月6日,台风"尤特"已在珠江口北岸登陆,可是7月8日却在广西近海普遍引起20cm以上增水。7月2日18时,台风"榴莲"已经在广西登陆,但是西传的陆架波使广西沿岸发生很强的西向流,表层地转流流速接近92cm/s。广西沿岸增减水除去台风直接与间接作用外,还有地形的影响与大气重力波的强化作用。

Fluctuation of water level in Guangxi near coast is mainly caused by typhoon-induced storm surges. Influenced by typhoon, the maximum increase and decrease in the water level in Beihai Observation Station over last 42 years are 1.45 m and --1.87 m. The water level always decreases at first and then increases in Guangxi near coast controlled by tracks of typhoons. Besides, indirect influence of westward coastal-trapped wave along Guangdong continental shelf also affects the water level greatly. A portion of westward coastal-trapped wave directly passes through the Qiongzhou Strait into the Beibu Gulf, and the other portion moves around the southern part of Hainan Island into the Beibu Gulf in a clockwise manner. On July 6, 2001, though typhoon Utor landed at the northern part of the Pearl River Estuary, it widely induced a 20 em increase in water level in Guangxi near coast on July 8. At 18：00 of July 2, 2001, though typhoon Durian landed in Guangxi, the westward coastal-trapped wave led a strong westward flow along Guangxi coast, and the geostrophic flow＇s velocity in the surface reached 92cm/s. Apart from direct and indirect influence of typhoon on the fluctuation of water level along Guangxi coast, the particular topography and atmospheric gravity waves also have an effect on the fluctuation of water level.