一次台风过程对西北太平洋西边界流系源区影响的数值模拟研究

Impact of a typhoon process on the source region of Northwest Pacific western boundary current system

利用POM及其与WRF的耦合模式对"格美"台风影响下的该海区进行了5组数值模拟试验,在对结果分析的基础上,得到了西北太平洋西边界流系源区对此次台风过程的响应。研究表明:在台风影响下,最大风速区及热通量输送决定了海表温度(SST)降温中心范围,热通量的输送对SST的降低贡献超过16.7%;受此次台风影响的混合层(OML)加深、维持的时间为42 h,热通量对OML的加深有正作用,但不如风应力的贡献明显。台风移动方向右侧,OML加深范围更大,且SST最大降低区并不是OML最大加深区。此次台风过程对黑潮南向流的影响较弱,主要增加了海洋混合层的北向流流量。利用耦合模式,考虑了海气间的相互作用,在台风中心附近模拟出由于低压引起的海面升高现象。

The coupled model based on POM and WRF, has been developed to simulate the effect of ＂KEAMI＂ typhoon in the study area by the five experiments. The responses of the western boundary current systems in the northwest Pacific Ocean have been analysis. Results indicate that during typhoon process, the scope of SST falling is determined by the maximal wind and heat fluxes. The contribution of heat fluxes to SST cooling exceeds 16.7%. But, because of the ocean current, the SST cooling center is not simply located at the maximal wind or heat fluxes feeding area. The typhoon deepens and keeps oceanic mixed layer（OML） for 42 h. The heat fluxes have active impact on deepening OML, but the contribution is not same as wind. OML deepening is relatively larger on the right side of typhoon track, but the SST cooling area is not just the area of OML deepening. The mechanisms are the existence of the North Equatorial Current on the left side of typhoon and the cyclonic current, which enlarge the lateral mixture to prohibit the OML deepening through mixing the around warm water with the low level cool water. Meanwhile, the right side of typhoon track is far away from typhoon’s center and the lateral mixture is getting weak. Typhoon wind is the main reason of the appearance of cyclonic current and the ocean surface sink, while the heat flux have little impact on dynamic field. This typhoon has little impact on south current of Kuroshio Current, but mainly accelerates the north current in OML. The ocean energy is centralized in OML. When the north current speed added, the heat flux supplied to East China Seas have also been added and affected China climate. The coupled model including air-sea interactions have simulated the＂hydrostatic pressure＂where there is raising elevation around typhoon’s center because of low pressure.