Sudden Track Turning of Typhoon Prapiroon (2012) Enhanced the Upper Ocean Response.

Due to the change in environmental steering flow influenced by the surrounding synoptic systems, typhoon tracks often manifest sudden turnings, potentially prolonging the residence time of typhoon wind forcing and, thus, exerting a remarkable upper ocean response. Typhoon Prapiroon (2012) in the western North Pacific, had a very complex track and underwent two sudden-turning stages over its lifespan. On the basis of satellite and Argo float observations, this paper studies the surface and subsurface ocean environmental responses to Prapiroon. The observations show that the oceanic responses during the two sudden-turning stages of Prapiroon were much more remarkable than those in the straight-moving stage, including significant sea surface temperature (SST) cooling (similar to 7 degrees C), sea surface chlorophyll-a (Chl-a) concentration increase (>0.30 mg m(-3)), and sea surface height anomaly (SSHA) reduction (<-50 cm), compared with those in the straight-moving stage, with SST cooling weaker than 3 degrees C, Chl-a concentration increase less than 0.05 mg m(-3), and SSHA reduction less than -10 cm. By employing the three-dimensional Price-Weller-Pinkel (3DPWP) model to conduct a series of sensitivity experiments, we separate the contribution of the typhoon track's sudden turnings to the upper ocean response and find that the relative contributions of the two sudden turnings to SST cooling (sea surface salinity salinification) reached 38.4% (23.5%) and 46.8% (28.0%), respectively. In addition, the model experiments further show that the sudden turning could also induce stronger upwelling in the subsurface ocean. Our results demonstrate that typhoon track sudden turning could result in more kinetic energy input into the upper ocean, enhancing the physical and biological responses in the upper ocean.