氣候變遷對西北太平洋熱帶氣旋的影響; Tropical cyclone changes in the Western North Pacific under climate change simulations

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Title:	氣候變遷對西北太平洋熱帶氣旋的影響;Tropical cyclone changes in the Western North Pacific under climate change simulations
Authors:	楊承道;Cheng-tao Yang
Contributors:	大氣物理研究所
Keywords:	氣候變遷;熱帶氣旋;climate change;tropical cyclone
Date:	2008-06-27
Issue Date:	2009-09-22 09:43:40 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究使用德國馬克斯-普朗克氣象研究所(Max Plank Institute for Meteorology)發展出來的第四版海-氣耦合模式ECHAM4，對IPCC訂出的溫室氣體排放A2、B2情境，模擬現在與未來氣候變遷之結果進行分析。從模擬結果發現，在溫室氣體濃度上升的情況下，西北太平洋的大尺度氣候場會有下列改變:(1)海溫會逐漸上升，(2)副熱帶高壓脊西伸，(3)中、低對流層相對濕度增加，(4)對流層的溫度上升，(5)沃克(Walker)環流減弱，(6)菲律賓附近的季風槽減弱，(7)南海附近的垂直風切減弱等現象。此外，比較A2、B2情境的氣候場變化差異，發現兩者皆呈現一致的變化趨勢，不同的是A2情境的變化量會比B2情境還大一些。分析從模式中定義出的熱帶氣旋個案，結果發現西北太平洋熱帶氣旋的個數會隨著溫室氣體濃度上升而減少，這可能和對流層增溫以及沃克(Walker)環流的減弱，加上海溫上升使洋面蒸發作用較旺盛，使水汽更容易在大氣中停留，再加上中、下對流層相對濕度的增加，讓大氣處於暖、濕的狀態，促使上、下層的溫度遞減率減少，垂直穩定度增加，使對流不易產生有關。也發現熱帶氣旋往北轉往高緯區的路徑有往西南偏之情形，可能原因為副熱帶高壓脊的西伸與較高緯區的東風駛流距平(即西風減弱)所造成。此外，還發現熱帶氣旋的生命期有隨溫室氣體濃度的增加而增長的趨勢，至於熱帶氣旋的風速與渦度強度則是呈現減弱的情形，但由於熱帶氣旋生命期增加與強度的減弱現象，可能會受到大尺度氣候場的年際變化以及使用的模式解析度和研究的方法不同之影響而有所差異，因此還需更進一步研究。 This study uses the Max Plank Institute (MPI) coupled model (ECHAM4/OPYC3) to simulated the IPCC A2 and B2 global warming scenarios. We discuss the total number, lifetime, intensity, track variation of tropical cyclones under different climate scenarios in the Northwest Pacific Ocean. According to the results, we find that when greenhouse gases increase, there are several changes occured in the Northwest Pacific Ocean. (1) Sea surface temperatures increase. (2) Subtropical high ridge extends westward. (3) Relative humidities of lower and middle troposphere increase. (4) Temperatures increase in troposphere. (5) Walker circulation weakens. (6) Monsoon trough weakens in the South China Sea and Philippines region, and vertical wind shear weakens over the South China Sea. In addition, comparing the difference between A2 and B2 scenarios, we find that the changes of climate trend in B2 are almost the same as A2, but the amplitude in A2 is larger. Furthermore, we find that the total number of tropical cyclones decrease in the Western North Pacific under the A2 and B2 simulations. This reduction is associated with the increase of sea surface and air temperatures. The weakening of Walker circulation will increase water vapor in atmosphere. These processes will make atmosphere warmer and more moisture. This in turn increases the static stability of the troposphere. The process restrict the convection activity and hence reduce the total number of tropical cyclones. In addition, the northeastern recurving tracks of tropical cyclones shift southwesterly. This attributes to westward extend of the subtropical high ridge and weakening of westerly steering flow in middle latitude. Finally, the lifetime and intensity variation of tropical cyclones under the A2 and B2 climate change simulations may be affected by the differences in method, model and atmosphere interannual variability. In these part of tropical cyclone characters, we still need further study to prove.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

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