氣膠遠程效應對熱帶降雨變異之影響及機制探討

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Please use this identifier to cite or link to this item: https://irlib.pccu.edu.tw/handle/987654321/27712

Title:	氣膠遠程效應對熱帶降雨變異之影響及機制探討 The Remote Influence of Aerosols on Tropical Precipitation Anomaly and the Possible Mechanisms
Authors:	王嘉琪
Contributors:	大氣科學系
Keywords:	氣膠氣候趨力氣候變遷降雨變異濕靜能氣候模擬
Date:	2014-08
Issue Date:	2014-08-07 11:23:48 (UTC+8)
Abstract:	氣膠是影響大氣水文循環和輻射平衡的關鍵因素之一，可以吸收和散射太陽輻射（直接效應），也可以成為雲凝結核（間接效應），進而改變雲與降水。以往對氣膠氣候趨力的研究多半只針對氣膠的直接與間接效應討論，也就是說氣膠只會在局部地區產生影響。但是初步研究已經指出氣膠可能會經由改變對流層溫度與水氣的空間分佈，進而影響熱帶降水，目前學界對這類遠距離的影響所知甚少。由於氣膠對溫度及濕度的整體效應在初步研究結果中顯示出全球性的降溫與濕度減少的趨勢，此空間分佈及變化趨勢恰好與全球暖化造成的趨勢相反。我們知道傳統的氣膠效應由於空間及時間尺度的關係，不應該與全球暖化效應互相抵銷，但是本研究有興趣的氣膠遠程影響卻可能可以透過類似全球暖化影響熱帶降雨的機制來作用。相關的機制有異常粗濕穩定度機制與 upped-ante機制，此兩機制分別針對對流中心與對流邊緣區討論，由於熱帶大氣必須維持對流準平衡，對流中心及邊緣區將分別出現降雨增加及減少的變化趨勢，也就是『富者越富』的現象。本計畫將選用 CMIP5中的四個氣膠模擬進行水氣及濕靜能收支分析，檢驗氣膠遠程影響的可能機制與詳細的發生過程，期能對氣膠氣候趨力有更進一步的了解。 Aerosols are one of the key factors that influence the hydrological cycle and radiation balance of the atmosphere. They can absorb and scatter solar radiation (direct effect), and become cloud condensation nuclei (indirect effects). Both types of effects confined the aerosol impacts on climate as regional impacts, rather than global. Therefore, conventional thoughts state that the aerosol forcing (overall is cooling) cannot reduce the warming by green house gases which is a global effect. Recently, some preliminary studies have pointed out that aerosol may have remote-impacts on tropical precipitation by changing the tropospheric temperature and moisture distribution. This aerosol remote-impact has not been discussed in details before. Because the modified temperature and moisture fields are also globally distributed, it is suggested that aerosol remote-impact may work by similar mechanisms as global warming effects. The mechanisms proposed here are the anomalous gross moist stability mechanism and the upped-ante mechanism. These two mechanisms focus on convective area and the edge of the convective area, respectively. For the tropical atmosphere to maintain convective quasi-equilibrium, the convective area will have enhanced precipitation, and the edge of the convective are will have weakened precipitation. This is the so-called “rich-get-richer mechanism”. This proposal selects four aerosol-forcing experiments from CMIP5 and does the moisture and moist static energy budget analysis to investigate possible mechanisms that may cause aerosol remote-impact on tropical precipitation. The results of this research may extend our understanding on the aerosol climate forcing.
Appears in Collections:	[Department of Atmospheric Sciences & Graduate Institute of Earth Science / Atmospheric Science ] project

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