| 摘要: | 間熱帶輻合帶（ITCZ）為大氣中主要的結構性系統之一，在地球能量收支與水循環部分扮演極重要的角色。然而，吾人對於它的動力過程仍然所知有限，包括破碎、形成的機制、常見的緯度、垂直結構與其他熱帶現象，如：季內震盪(Madden-Julian Oscillation, MJO)或聖嬰現象(El Nino-Southern Oscillation)之間的關係。此計畫將增進吾人對熱帶動力與ITCZ的基礎瞭解。 此計畫大至可分為三部分：第一部份針對ITCZ的演變特性（破碎與重建的週期性變化）探討其動力與水氣作用的過程。將使用由加州大學洛杉磯分校(UCLA)發展的一個中等複雜程度的大氣模式（the quasi-equilibrium tropical circulation model 1 version 2.3 , QTCM1V2.3）為主要研究工具。 第二部分著重在探討海氣交互作用，將使用衛星觀測資料進行客觀分析。目前已經有數份研究使用波譜法成功找到熱帶波動的訊號，包括ITCZ與較為微弱的熱帶擾動。我們預期將找到一些參數來描述海洋對大氣高頻變化的反應，及隨後大氣感受到海洋變化時的反應。ITCZ與其他熱帶天氣或氣候現象的交互作用也將被仔細討論。 第三部分則延伸與應用前兩部分的成果，希望利用衛星觀測提供的資訊，建立一簡單海洋經驗模式以供進一步的研究。此計畫將試圖解答以下科學問題：（1）ITCZ的生命週期是透過何種機制演變與運作；(2)海洋(SST或海洋動力)在ITCZ生命週期中扮演什麼樣的角色；(3)ITCZ如何反饋海洋的變化；(4)ITCZ 如何與其他熱帶波動現象互相影響
The Inter-Tropical Convergence Zone (ITCZ) is a major organized system in the atmosphere in terms of Earth's energy budget and hydrologic cycle. However, the dynamics of the ITCZ is not well understood, such as the breakdown and formation mechanism, preferable location, vertical structure, and interactions with other tropical phenomena, such as the Madden-Julian Oscillation (MJO) and El Nino-Southern Oscillation (ENSO). This project will contribute to fundamental knowledge of the tropical dynamics and the ITCZ. The work we propose can be divided into three parts. The first part investigates the effects of dynamical processes and moisture processes on the ITCZ characteristics, including its life cycle, breakdown process, and formation process. An intermediate atmospheric model, the quasi-equilibrium tropical circulation model 1 version 2.3 (QTCM1V2.3) developed in the University of California, Los Angeles (Neelin and Zeng 2000; Zeng et al. 2000) will be employed. The second part focuses on the air-sea interaction by using remote sensing datasets, such as QuikSCAT wind and TMI SST. We will use advanced statistical methods to objectively analyze the datasets. The wavenumber-frequency spectrum analysis has been employed to identify tropical waves, including ITCZ and tropical disturbances, from National Ocean and Atmosphere Administration (NOAA) outgoing longwave radiation (OLR) and reanalysis dataset. Remote sensing datasets are only available on oceans and often contains a lot of missing values; therefore, a substantial modification to the methodology will be needed to allow missing values in the analysis. We expect to find some parameters that describe the ocean responses, including ocean dynamics and SST changes in the top layer, due to ITCZ activities. In addition, to understand how the atmosphere responses to these ocean changes in return. The relationship between the ITCZ and other tropical phenomena will be discussed as well. The third part continues the research about air-sea interaction and further investigates the mechanisms that induce the interaction. In the beginning, the QTCM1 will be coupled with a simplified ocean model which is an empirical model instead of a full ocean model. This empirical ocean model will be composed according to the parameters found in the second part. However, we do not exclude the possibility to use a more complete ocean model. The purpose of using empirical ocean model is to simplify the model design that may help the interpretation of the results. A more advanced ocean model will be used in the later part when we consider performing more realistic simulations. Our findings may be applied to further understand the south-westerly flow associated with typhoons and benefit on the human society. The scientific questions we will address are (1) through what mechanisms the ITCZ lifecycle evolves as it is observed, (2) what is the role of the ocean in the ITCZ life cycle, (3) how the ITCZ responses to the changes of the ocean, and (4) how the ITCZ interacts with other tropical wave phenomena. |
