| Summary: | 博士 === 國立中央大學 === 大氣物理研究所 === 103 === The rightward tendency (in northern hemisphere) of enhanced phytoplankton bloom often observed in the wake of a tropical cyclone has commonly been attributed to the rightward bias of mixing due to stronger wind and wind-current resonance. We demonstrated using a high-resolution biophysical model (ATOP-NPZD) that vertical mixing alone resulted only in weak asymmetry. The bloom asymmetry was caused instead by intense sub-mesoscale recirculation cells produced on the right side, rightward shift of cool isotherms, and spin-up of a subsurface jet. We showed using a two-time scale asymptotic expansion that these slower evolving features were forced by resonance Reynolds stresses of the energetic and rapidly oscillating near-inertial internal waves.
In addition, we further developed and used a new ocean physical - biogeochemical coupled model (ATOP-Photo-SiNE) which simulated a better result of long time period. During 7~10 days after tropical cyclone passed, the diatom would grow fastly and then sink from surface layer that quickly reduced the DIN (dissolved inorganic nitrogen) concentration of surface layer that inhibited the development of phytoplankton bloom. Therefore, the surface chlorophyll-a concentration didn’t overgrow and fastly return to normal conduction. Our result suggests that the biological responses also plays an important role in marine biogeochemical feedback. The participation of diatom in the more complex Photo-SiNE model is necessary for investigating the long-term biogeochemical response induced by tropical cyclone.
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