| 摘要: | 了解及預報颱風與海洋的耦合反應是海洋大氣科學研究中最有挑戰性的問題之一。颱風不僅影響海面流場及垂直混合作用，也產生巨大波浪與上層海洋的次中尺度環流胞，這些複雜的海洋動力過程將會導致颱風尾流的海表溫冷卻及藻華現象。海表面暖濕空氣經由向氣旋中心的海氣通量傳颱風眼內，改變颱風內部的位渦並持續增強颱風，這些持續的海氣交互作用進而產生耦合效應，但我們對其中複雜的物理動力過程理解仍然有限。在前人的研究已顯著改善颱風的路徑預報，而颱風內部的動力過程、大尺度的背景場與海面溫度變化讓準確的強度預測依舊十分困難。目前只有少數幾個預報模式考慮到海氣耦合作用[例如HWRF，WRF與POM耦合]，而且氣象局主要使用非耦合模式來預報，因此耦合預報模式的發展與研究已刻不容緩。在科技部過去四年補助下，我們發展第一套台灣海洋預報系統(ATOP)，每天預報涵蓋太平洋的洋流、溫鹽、波浪、潮汐及風暴潮等，且總共發表35篇SCI文章。此提案為1年期計畫，以ATOP與WRF為基礎建立颱風-海洋耦合預報系統 (CTOP)。計劃將研究(1)氣旋對海洋不同尺度與領域的影響; (2)以位渦及海氣交互作用來探討氣旋的增強機制，預期將提高台灣的氣旋預報能力，並對社會與經濟產生貢獻。 ;One of the most challenging problems in ocean, atmosphere and climate research is to understand and forecast the coupled response of ocean and tropical cyclones (TCs or typhoons). TC drives ocean currents and mixing [Price 1981; Price et al. 1994], waves [Holthuijsen et al. 2002; Moon et al. 2004; Oey et al. 2008], and sub-mesoscale cells [Huang and Oey 2015; Lin & Oey 2016], resulting in a myriad of complex upper-ocean processes which cool the SST and support phytoplankton bloom [see reference in Huang and Oey 2015]. In turn, the ocean influences air-sea fluxes, hence the moist air that spirals into the eye of the storm in the surface boundary layer [Riehl 1963; Emanuel 1986], modifying the potential vorticity (PV) structure of the TC's hot tower and its intensity [Sun and Oey 2015]. The altered surface fluxes feed back into the ocean, continuing the coupled loop. Despite the importance of air-sea coupling to upper-ocean response and TCs, our understanding of the complex physical processes remains limited [Bao et al. 2000; Chen et al. 2007; Lee and Chen 2012]. Moreover, while the skill in forecasting TC tracks has steadily improved, as TCs are primarily steered by large-scale wind [Marks and Shay 1998; Chen et al. 2006], the intensity forecast has not [Rogers et al. 2006; Houze et al. 2007; Rappaport et al. 2009; Gall et al. 2013; Rios-Berrios et al. 2014], since intensity depends on inner-core dynamics [Marks and Shay 1998; Houze et al. 2007], environment [Zeng et al. 2007; Hill and Lackmann 2009] and sea surface temperature (SST) [Emanuel 1999; Schade and Emanuel 1999; Lin et al. 2008; Emanuel et al. 2004]. A few operational forecast models are coupled [e.g. HWRF, coupling WRF with POM], and in Taiwan uncoupled typhoon forecast model is used at CWB. Under a previous support from MOST, we have successfully completed the development and testing of Advanced Taiwan Ocean Prediction (ATOP) model. ATOP now routinely forecasts sea level (waves, tides & storm surge), currents, temperature and salinity for the entire North Pacific Ocean. Since 2013 ATOP research activities have resulted in 35 SCI publications covering a broad range of topics from physics to biology, and from coastal circulation and winds in the seas around Taiwan, to Kuroshio, basin and climate-scale processes. This proposal seeks a 1-year support to continue developing and testing a Coupled Typhoon-Ocean Prediction (CTOP) model based on ATOP and WRF. The overarching goal is to validate a prototype CTOP, understand how to produce accurate intensity forecasts, and conduct research focusing on upper-ocean and typhoon processes (rather than on e.g., data assimilation and initializations). We plan to study (i) ocean's mixed-layer, sub-mesoscale physics and biogeochemical process under the TC and its wake, and how they feedback into the storm; and (ii) coupled TC-intensification process as a PV-enhancing, air-sea interactive process [Sun and Oey,2015]. Besides providing insights into ocean-typhoon coupling processes, the proposed work clearly will advance Taiwan's typhoon and ocean forecasting capability to a new level, with anticipated benefits to society and commerce. |
