南海之熱帶氣旋所引起強烈降溫作用與藻類繁生之研究：左右不對稱之機制探討及生地化模組之改進;Tropical cyclone induced strong cooling and phytoplankton bloom in the South China Sea : A mechanistic investigation of the asymmetric response and improvement of the biogeochemical module

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Title:	南海之熱帶氣旋所引起強烈降溫作用與藻類繁生之研究：左右不對稱之機制探討及生地化模組之改進;Tropical cyclone induced strong cooling and phytoplankton bloom in the South China Sea : A mechanistic investigation of the asymmetric response and improvement of the biogeochemical module
Authors:	黃士銘;Huang,Shih-Ming
Contributors:	大氣物理研究所
Keywords:	熱帶氣旋;藻類繁生;左右不對稱;生地化模式;tropical cyclone;phytoplankton bloom;asymmetric;biogeochemical model
Date:	2015-07-25
Issue Date:	2015-09-23 10:06:20 (UTC+8)
Publisher:	國立中央大學
Abstract:	熱帶氣旋從北半球海面經過後，所引起右側降溫作用與藻類繁生現象經常被觀測到，並且已經普遍被歸納為: 氣旋右側較強的風場與風-海流的共振作用，導致此往右側傾斜的趨勢。然而，我們使用高解析度的海洋物理-生地化(ATOP-NPZD)耦合模式，發現單獨的垂直混合過程只會產生弱的不對稱現象。進一步的研究結果顯示，不對稱的藻類繁生現象是由於右側強烈的次中尺度(sub-mesoscale)的垂直環流胞、往右側傾斜之冷水的等溫線與在次表層形成的噴流一起共同作用所造成。當我們使用一個雙重時間尺度的漸進展開分析，發現這些較緩慢發展的特徵都是經由，活躍和快速振盪的近慣性內波所引起之Reynolds切應力的共振所導致。值得一提的是，雖然這過程較慢，但是這些現象都發生在一周之內。除此之外，我們進一步發展使用新的海洋物理-生地化耦合模式(ATOP-Photo-SiNE)，我們發現在較長期的的模擬中，效果較佳，其結果顯示在熱帶氣旋過後的7-10天之內，矽藻會先大量的生長，然後再自表層水體沉降，如此一來能較快速降低表層的營養鹽，抑制海表面浮游植物繼續的繁生，使得熱帶氣旋過後一星期以上海表面的Chl-a濃度不會過度生長而且能較快速的回復正常狀態。證明海洋生物的反應也扮演了重要的海洋生地化回復機制。因此，在模式中擁有矽藻部門之較複雜的Photo-SiNE生地化模式，對於探討熱帶氣旋所引起較長期海洋生地化之反應是必須的。;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.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

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