Tiedtke積雲參數法的逸入逸出率對於MPAS模式中DYNAMO時期MJO模擬的影響

Abstract

此研究以積雲參數法New Tiedtke scheme為核心，探討DYNAMO期間MJO的對流過程模擬。內容分為兩部分，一個是New Tiedtke scheme offline診斷分析，一個是MPAS全球模式模擬。 offline診斷分析中，探討大尺度環境和強迫項如何驅動積雲參數法(New Tiedtke scheme)產生單方向的反應，之後再計算微物理參數法(WSM6)，完成模式中跟雲有關的兩個物理參數法。過程中沒有計算大尺度動力和其餘物理參數法(輻射、邊界層)，較全球模式簡單。New Tiedtke scheme的淺雲扮演著將邊界層的水氣向上傳送的角色; 深對流雲對整層大氣效應為加熱和變乾，所產生的降雨和觀測一致。後續計算微物理參數法offline，如將積雲參數法對大尺度溫度和水氣的改變加入後，淺雲的濕化讓微物理參數法產生更多降雨，深對流雲的加熱和變乾讓微物理參數法產生較少的降雨。offline診斷中的積雲參數法降雨和微物理參數法降雨的比例約為10:1。 MPAS全球模式模擬，以預設New Tiedtke scheme、New Tiedtke scheme逸入率乘上1.8倍、New Tiedtke scheme改變逸出率，三組實驗進行MJO模擬。2011年10月15日到31日模擬的大致情況為，預設實驗中，在中印度洋對流零散大致以日夜週期一天的時間尺度產生向東傳遞的訊號。增加逸入率實驗，造成環境場較乾時對流更不易發展，能讓對流往濕區集中使組織性更好，增加逸入率對於Kelvin wave的模擬較好。逸出率實驗，積雲參數法的深對流雲上衝流過程中界定次網格雲和次網格環境的差異到達一定小時，將雲內性質逸出改用大尺度動力和微物理參數法操作極端深對流雲區，逸出率類似於部分關閉積雲參數法，此實驗能夠模擬出正確MJO生成時間。開關積雲參數法的差異以處理積雲上衝為例，在積雲參數法中由逸入逸出(E、D)控制質量通量隨高度分布 (∂M/∂Z) 不對時間做微分，故積雲上衝毋需耗時，再關閉積雲參數法時使用大尺度上升運動(W)隨著模式積分具有時間上的連續性。而質量通量型積雲參數法使用逸入逸出率對於積雲發展的相關議題有著基本操作上的難度。 預設、逸入、逸出三組實驗中，積雲參數法和微物理參數法控制熱帶對流雲的角色也跟著改變，兩者之間的配合為文章中深入探討的重點。

In this article, using cumulus parameterization New Tiedtke scheme to discuss convection process is main focus. Content is composed of two parts. One is New Tiedtke scheme offline analysis, another is GCM simulation. The purpose of Offline analysis is to know how cumulus parameterization response according to given large scale forcing. After cumulus parameterization, also calculate microphysics scheme. Difference from GCM is there are no large scale dynamic and other physics scheme in calculating routine such that offline analysis is rather simpler than GCM. In offline analysis, shallow cloud transport water vapor from boundary layer to higher free atmosphere, can moisten atmosphere .To large scale environment, deep cloud response is drying and heating and produced precipitation is well match with TRMM observation. Finishing cumulus scheme, then do microphysics scheme calculation. If adding cumulus scheme response to large scale moisture and temperature field, in shallow cloud region microphysics scheme can produce more rain, in deep cloud region microphysics scheme produce less rain. The ration between cumulus Offline rain and microphysics Offline rain is about 10 to 1. MPAS GCM simulation have three experiments, default New Tiedtke scheme, entrainment multiply 1.8, and modified detrainment. In defalut experiment convection are scatter, in entrainment experiment convection are more organized, and detrainment experiment can simulate MJO accurate initiation. The effect of increased entrainment rate is deep convection cannot develop in dry region, deep convection will aggregate to moist region ,convection become more organized. Detrainment experiment is similar to turning off cumulus parameterization in extreme deep convection region. In cumulus parameterization updraft once the difference between subgrid-scale cloud and subgrid-scale environment is small, detrain and switch to large scale dynamic and microphysics scheme. Using large scale dynamic and microphysics scheme control extreme convection region. This three experiments show cumulus and microphysics scheme both can control tropical convection but operation methods are different, and the interaction between cumulus parameterization scheme and microphysics parameterization scheme are also main topic in this article.