本論文主要貢獻有三個：首先，我們檢驗了控制深對流和淺對流垂直濕靜能輸送差異的因素。當最大垂直速度落在高(低)對流層時，如西(東)太平洋ITCZ區，有利於濕靜能輸出(入)。分析顯示，垂直濕靜能輸送的正負號主要由垂直水氣輸送項決定，其值大小對垂直運動的結構非常敏感。第二，我們利用CESM探討了模式空間解析度對對流垂直結構之影響，包含400km，200km，100km和50km四種解析度的敏感度實驗。實驗結果顯示，較高的模式解析度往往產生更多的淺對流，而較粗糙模式解析度傾，往往產生較少淺對流。更多的淺對流可增強降水頻率和強度，以及總降水量。瞭解上述結果對於氣候模式應用極為重要，因為目前氣候模式仍然使用較粗略的空間解析度進行模擬和推估未來氣候。最後，我們比對了13個CMIP5耦合模式深、淺對流的垂直結構特徵，並討論淺對流結構差異對熱帶降水模擬的影響。;This thesis aims to elucidate the impacts of vertical structure of convection on tropical climate. We focus on the partition between deep (top-heavy) and shallow (bottom-heavy) convection and how its change affects the moist static energy (MSE) transport and precipitation over the western and the eastern Pacific ITCZs. Both reanalysis data and model simulation output - using the Community Earth System Model (CESM) - are utilized to explore the mechanisms behind such change.
The thesis provides three main contributions. Firstly, we examined the controlling factors of the column-integrated vertical MSE advection for both deep and shallow convection. The MSE budgets are computed over the western Pacific and the eastern Pacific ITCZs, dominated respectively by a top-heavy and bottom-heavy structure of convection. A top-heavy (bottom-heavy) structure of vertical motion favors an export (import) of MSE and a positive (negative) value of the vertical MSE advection. It was shown that the sign of vertical MSE advection is determined mainly by the vertical moisture transport whose magnitude is very sensitive to the structure of vertical motion. Secondly, we introduced the impacts of model spatial resolutions on the vertical structure of convection in the CESM. Four spatial resolutions, 400 km, 200 km, 100 km and 50 km, are used. Higher resolution tends to produce more partition of shallow convection, while coarser resolution inclines to produce less. More partition of shallow convection tends to enhance precipitation frequency and intensity, as well as the total precipitation amount. This is particularly important in modeling tropical climate and projecting future climate change in which long term model runs are often performed with coarser resolutions. Lastly, we presented the vertical structure of deep and shallow convection in the Coupled Model Intercomparison Project phase 5 (CMIP5) models, that takes into account the impacts of shallow convection depth on precipitation.
