熱帶對流層氣溫之主要擾動有多接近對流準平衡?;How Close Are Leading Tropical Tropospheric Temperature Perturbations to Those under Convective Quasi-Equilibrium?

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题名:	熱帶對流層氣溫之主要擾動有多接近對流準平衡?;How Close Are Leading Tropical Tropospheric Temperature Perturbations to Those under Convective Quasi-Equilibrium?
作者:	李羿賢;Li, Yi-Xian
贡献者:	國際研究生博士學位學程
关键词:	對流準平衡;熱帶對流層氣溫;Convective Quasi-Equilibrium;Tropical Tropospheric Temperature
日期:	2022-06-29
上传时间:	2022-07-13 21:30:14 (UTC+8)
出版者:	國立中央大學
摘要:	在對流準平衡理論中，熱帶對流層之溫度擾動預期受對流約束而遵循特定的垂直剖面(在本論文中稱其為 A-profile，常近似於濕絕熱線間剖面相減)。此研究發現在對流情況下：基於濕靜能守恆所導出的理想化A-profile與有/無將逸入納入計算的氣柱溫度擾動之差異皆不大—端賴於深對流好發於低對流層水氣接近飽和之時，從而大限度地減少了逸入對於對流層溫度的影響。因此，鑑於觀測氣溫剖面的假絕熱擾動法便提供了精簡實用的 A-profile計算基準。在低於中性浮力高度(LNB)的大氣中，我們將A-profile與 ERA-Interim 再分析和 AIRS 衛星反演資料中經驗正交函數的首要模式(TEOF1)進行比較：具有高 LNB（通常高於400 hPa）的 TEOF1與 A -profile在垂直方向上存在高空間相關係數（~0.9），表明在有利於深對流的環境中：對流層溫度擾動傾向於符合對流準平衡假設。反之，較低的相關係數往往發生在氣候上 LNB 較低、不利於深對流的地區。我們亦發現若屏除低 LNB 之時刻，熱帶地區整體的垂直空間相關係數將顯著增加。鄰近LNB的溫度擾動存在對A -profile的負偏差值—即對流冷頂(Convective cold top)現象—且LNB越高，其偏離程度越大。在相關係數較低的地區可觀察到TEOF1對A-profile的偏移量在600 hPa以下呈S形，且常伴隨著較乾燥的低對流層。即使垂直空間相關性和TEOF1可解釋變異量在較短的時間尺度上趨於降低，上述所有研究成果自日至月的廣泛時間尺度上都是穩健的。;In convective quasi-equilibrium theory, tropical tropospheric temperature perturbations are expected to follow vertical profiles constrained by convection, referred to as A-profiles here, often approximated by subtractions between moist adiabats. This study finds that differences between an idealized A-profile based on moist-static energy conservation and temperature perturbations derived from entraining and non-entraining parcel computations are modest under convective conditions—deep convection mostly occurs when lower troposphere is close to saturation, thus minimizing the impact of entrainment on tropospheric temperature. Simple calculations with pseudo-adiabatic perturbations about the observed profile thus provide useful baseline A-profiles. We compare the first EOF mode of tropospheric temperature (TEOF1) from the ERA-Interim reanalysis and AIRS retrievals below the level of neutral buoyancy (LNB) with these A-profiles. The TEOF1 profiles with high LNB, typically above 400 hPa, yield high vertical spatial correlation (~0.9) with A-profiles, indicating that tropospheric temperature perturbations tend to be consistent with the quasi-equilibrium assumption where the environment is favorable to deep convection. On the contrary, lower correlation tends to occur in regions with low climatological LNB, less favorable to deep convection. We also find that excluding temperature profiles with low LNB significantly increases the tropical mean vertical spatial correlation. The temperature perturbations near LNB exhibit negative deviations from the A-profiles—the convective cold top phenomenon—with greater deviation for higher LNB. One can observe that in regions with lower correlation, the deviation of TEOF1 from A-profile shows an S-like shape beneath 600 hPa, usually accompanied by a drier lower troposphere. All the above research findings are robust across a wide range of timescales from daily to monthly, although the vertical spatial correlation and TEOF1 explained variance tend to decrease on short timescales.
显示于类别:	[地球系統科學國際研究生博士學位學程] 博碩士論文

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