Browsing by Author "潘任飛"

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    Estimation of upper-ocean thermal structure in the North West Pacific Ocean by satellite remote sensing and its application to typhoon intensity change
    (2005) 潘任飛; PUN, IAM-FEI
    Lack of the information on upper-ocean thermal structure is one of the identified major reasons causing unsatisfactory typhoon intensity forecast. Therefore it is critical to study the relationship between upper-ocean thermal structure typhoon intensity change. This study uses a two-layer reduced gravity ocean model (TLM_NWPO), TOPEX/Poseidon and JASON-1 sea surface height anomaly data, TRMM/TMI sea surface temperature data and climatological ocean data estimate upper-ocean thermal structure in the Northwest Pacific Ocean. The estimated profiles were validated by 2258 co-located and near co-incident in situ profiles from the Global Temperature and Salinity Profile Program (GTSPP) and the ARGO floats. It is found that the two-layer reduced gravity model is not always applicable in the entire NWPO; depends on location and month. The ‘safe zones’ where the TLM_NWPO can accurately use are defined. It is encouraging to find that most category-4 and 5 typhoons intensify in the ‘safe zones’, thus we can apply the estimated profiles to study its association with typhoon intensity change. All 33 intense and super typhoons (category-4 and 5) occur during the typhoon season (May-October) in the past 6 years (1999-2004) are studied. The sensitivity of four possible parameters (pre-typhoon SST, inner-core SST cooling, pre-typhoon Tropical Cyclone Heat Potential and inner-core Tropical Cyclone Heat Potential) are assessed. It is found that the inner-core SST cooling is the most sensitive parameter and typhoon stops intensification when the inner-core SST cooling exceeds 2.5℃. In contrast, the often emphasized pre-typhoon TCHP is found to be insensitive. It is found that TCHP is over-supplying parameter and the available TCHP is always at least an order higher than typhoons can extract, suggesting that TCHP should not be a limiting factor controlling typhoon intensification.
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    利用遙測估計西北太平洋上層海洋溫度結構
    (2005-10-19) 林依依; 潘任飛; 吳朝榮
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    西北太平洋颱風潛熱(Tropical Cyclone Heat Potential TCHP)之研究
    (2004-05-20) 潘任飛; 林依依; 吳朝榮
    在近來的研究中有相當多的證據顯示颱風強度的增加與海洋中的暖特徵現象 (warm oceanic features)有關，並且利用颱風潛熱(TCHP)來代替傳統的海水表 面溫度(SST)來研究颱風的強度(Shay 2000, Goni & Trinanes 2003)，因為 SST只能代表的海水表面溫度而無法代表上層海洋的垂直結構(Upper ocean thermal structure)，因此TCHP能夠清楚地描述海洋的暖特徵，如暖渦(warm core ring, WCR)；早在1972年Leipper就把TCHP 定義出來，但由於當時沒有衛 星資料的幫助，一直無法運用，直到近年由於衛星遙測的進步，才被開始被應用 ，TCHP的定義是從海面到26度C等溫線的垂直溫度積分，如下：Q/sub H/(x,y,t)=.rho.C/sub p/.int./sup 0//sub (Y=26)) .DELTA.T(x,y,z,t)dz每 年有不少的強烈颱風在西北太平洋(Northwest Pacific Ocean, NWPO)產生出來 ，但目前全球對颱風強度的預測並不是很理想，因此藉著研究NWPO的TCHP和 TCHP與颱風之間的關係來提昇我們對颱風強度之預測。本研究是採用美國海軍實 驗室(US Naval Research Laboratory)所發展的三維數值模式(NPACNFS, North Pacific Ocean Nowcast/Forecast System)，此模式是修改自Princeton Ocean Model (Blumberg and Mellor, 1987)，使模式能作資料同化(data assimilation)，其作同化的資料有T/P的SSHA和由衛星所得到的海表面溫度 (SST)。整個太平洋模式蓋了16度S~60度N，99度E~77度W的區域，而模式的垂直 解析度是用26層的sigma-levels組成，在上層海洋的分層數比較密，所以此模式 對上層海洋的解析度比較高，有利於對上層海洋的研究。利用此模式的結果，可 以算出北太平洋的TCHP。本研究並把由NPACNFS 和由美國大氣海洋總署(AOML)利 用來two-layer reduced gravity model 計算出來2003 年夏天的TCHP作比較。