熱帶對流的水氣與能量輸送: 深-淺對流模之比較;Moisture and Energy Transports by Tropical Convection: Contrast between Deep and Shallow Convective Modes

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题名:	熱帶對流的水氣與能量輸送: 深-淺對流模之比較;Moisture and Energy Transports by Tropical Convection: Contrast between Deep and Shallow Convective Modes
作者:	陳怡蒨;Chen, Yi-Chien
贡献者:	大氣科學學系
关键词:	濕靜能;深對流;淺對流;Moist Static Energy;Top-heavy convection;Bottom-heavy convection
日期:	2018-07-05
上传时间:	2018-08-31 11:24:36 (UTC+8)
出版者:	國立中央大學
摘要:	本論文使用ERA-Interim氣象觀測再分析資料以及TRMM的衛星降水資料來探討氣候態平均下，熱帶地區深、淺對流的水氣與能量輸送及其物理機制。觀察熱帶地區主要的對流上升和下沉區，分析氣壓垂直速度來檢驗對流結構，並使用水氣、乾靜能和濕靜能收支，最終，我們在熱帶地區確定了四種類型的對流。在熱帶地區的四種類型對流結構中，第一斜壓模和第二斜壓模各有兩種。第一斜壓模為兩層結構，空氣低層輻合到對流中心，在高空輻散；第二斜壓模為三層結構，空氣在中層輻合（或輻散）並在下層和上層輻散（或輻合）。進一步研究不同類型的對流在氣柱中輸送水氣和濕靜能量（MSE）中的作用，我們發現第一斜壓結構的對流在水氣和MSE輸送之間表現出不同的趨勢，雖然在第一斜壓模中兩種類型的對流都傾向於濕化氣柱，但在傳輸MSE時常表現出相反的結果：Top-heavy結構(1a Type)傾向輸出氣柱MSE，導致大氣趨向穩定；Bottom-heavy結構(1b Type)傾向輸入氣柱MSE，導致大氣趨向不穩定。與此相反，第二斜壓模中水氣和MSE輸送呈現一致趨勢：空氣在中層輻散(2a Type)的結構中，水氣和MSE都是輸入的，導致大氣不穩定且濕化氣柱；空氣在中層輻合(2b Type)的結構中，水氣和MSE都是輸出的，導致大氣穩定且乾化氣柱。最後，我們分析水氣收支中各項對降水的貢獻，並針對這四種對流結構來探討熱帶對流區的降水種類。 ;In this thesis, we identified dominant modes of tropical convection based on the ERA-interim atmospheric data as well as the TRMM precipitation data and examined their roles in transporting moisture and energy in a climatological sense. Based on the technique of EOF decomposition and reconstruction, four major types of convection are identified in the Tropics. The first two types of convection exhibit a two-layer, the first baroclinic structure, with air converging into the convective center at low-levels and diverging aloft. The other two types of convection show a three-layer, the second baroclinic structure, with air converging (or diverging) at mid-levels and diverging (or converging) below and aloft. The roles of different types of convection in transporting atmospheric column moisture and moist static energy (MSE) are also examined. We find that the first two types of convection exhibit distinct tendencies between moisture and MSE transports, i.e., while both types of convection tend to moisten the atmospheric column, they show opposite signs in transporting MSE. A top-heavy convection exports the column MSE, resulting in a stabilization of the atmosphere; while a bottom-heavy convection imports the column MSE, resulting in a destabilization of the atmosphere. In contrast, the last two types of convection show a consistent tendency between moisture and MSE transports. That is, the convection with air diverging at mid-levels (positive mode) imports both the column moisture and MSE, resulting in a rapid destabilization of the atmosphere; while the convection with air converging at mid-levels exports both the column moisture and MSE, resulting in a quick stabilization of the atmosphere.
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