Study On Air-sea Interaction And Rapid Intensification In Typhoon Process

Air-sea interaction and rapid intensification(RI)are two important topics in typhoon process,this study investigates a typhoon case experienced extreme air-sea interaction process using a coupled air-sea-wave model and a case experienced RI process using a triply nested atmospheric model with finest 1.66 km resolution.The aim of this study is to explore the interactions of different parts and physical processes during typhoon process,and deepen our understandings of RI from different scales.This study investigates the mechanisms of sea surface cooling and the temporal and spatial distributions of cooling during typhoon Megi(2010).Results reveal that,the cooling is weak when typhoon moves at a high speed and the right side cooling is much stronger.When typhoon moves at a much slower speed,however,the cooling is much stronger and cooling in the center area is more obvious.Research of ocean vertical velocity reveals that,the right cooling bias is due to wind-flow resonance and the upwelling is significant due to Ekman pumping when the typhoon moves slowly.Further analysis reveals that,Megi impacts the ocean deeper than 700 m.The heat flux is reduced by 33% due to the sea surface cooling,and the typhoon intensity is largely reduced then.Ocean surface waves impact the surface wind structure,strengthen the inner-core latent heat flux.The waves also strengthen the ocean mixing,resulting in stronger cooling and the change of ocean flow direction.This study also investigates the RI process of typhoon Nepartak(2016).The results reveal that,Nepartak experiences its RI in a favorable large scale environment,and the RI can be divided into two stages,the asymmetric RI and axisymmetric RI.In the first stage,systemetic asymmetric structure and convective bursts are produced in the left side of vertical wind shear,as the shear rotates anti-clockwise,the convective bursts extent to the upshear direction,and the symmetry intensifies.In the second stage,the positive feedback is triggered,and the upper-level warm core is produced shortly,the sea surface pressure is largely reduced then.