“纳沙”台风引起北部湾沿岸风暴射流及其机制

Mechanism of Typhoon-Driven Storm Jet Driven by Typhoon Nesat in the Gulf of Beibu

基于FVCOM模式建立一个三维数值模型,对2011年“纳沙”台风登陆北部湾前后水位与流场变化进行了分析,并探究了风暴射流的生成机制。结果表明,广西近岸风暴射流的产生是对台风到来造成的水位起伏变化的一种正压响应;台风进入到北部湾期间,造成北部湾近岸水位先降低后升高,所导致的水位梯度差产生了驱动力,促使海水向西运动增强,从而导致在广西近海风暴射流的产生;台风登陆期间琼州海峡西向流流量增大到0.4 Sv以上,最大可达0.7 Sv;台风进入到北部湾后,促使琼州海峡西向流更多进入到北部湾,造成湾内正位涡输入增大,产生了气旋式环流来维持位涡平衡,同时气旋式环流也有利于向西运动的风暴射流增强;流经广西沿岸的风暴射流引起向西的水体输运可达0.2 Sv,对北部湾内营养盐以及污染物运移将产生重要影响。

Based on FVCOM model,a 3-D numerical model was established to research the change of the water level and flux field between typhoon Nesat landing the gulf of Beibu in 2011,and to discuss the mechanism of Typhoon-driven Storm Jet.The results show that the Typhoon-driven storm jet in Guangxi is a barotropic response to the fluctuation of water level caused by typhoon;The coast water level in the gulf of Beibu first decreased and then increased during the typhoon enter the gulf of Beibu,and then it results in a water level gradient generated a driving force,which enhanced the westward movement of the sea water,thus leading to the generation of typhoon-driven storm jet in the coastal area of Guangxi;the westward flow of Qiongzhou Strait increased to more than 0.4 SV,and the maximum was 0.7 SV during the typhoon Nesat;after the typhoon landing the gulf of Beibu,the westward flow of Qiongzhou Strait inflowed more into the gulf,which resulted in the increase of positive potential vortex input,cyclonic circulation was generated in the gulf to maintain the balance,and the cyclonic circulation is also beneficial to the enhancement of the typhoon-driven storm jet;the water transport caused by the typhoon-driven storm jet flowing through the coastal of Guangxi was up to 0.2 SV,which would affect the transport of nutrients and pollutants in the gulf of the Beibu.