The biophysical responses of the upper ocean to the typhoons Namtheun and Malou in 2004

The responses of the upper ocean to typhoons were investigated by the observations of sea surface wind (SSW), sea surface temperature (SST), sea surface height anomaly (SSHA), chlorophyll-a (Chl-a) and Argo floats. Typhoon Namtheun had notable impacts on the upper ocean along its track from July to August 2004. The local processes (entrainment and upwelling) dominated the upper ocean responses in the regions of the pre-existing cold eddy and beneath the typhoon track, where the observed locations of upwelling, SSHA changes, SST cooling, and Chl-a enhancement were consistent with each other. Besides, there were cold tongues extending from the cold centres. The trajectories of Argo floats, along with the cold tongues, indicated that the surface advections induced such non-local responses. On the other hand, the following weak typhoon Malou had few impacts on the upper ocean. Finally, the mechanisms of the Chl-a concentration enhancement were sketched as the effects of both the local upwelling and the non-local advection. This study implies that some non-local processes, e.g. horizontal advections, may play a notable role in the upper ocean responses to the typhoons.