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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/83110

    Title: 應用秩等級分布恆常性於氣候預測的可行性研究與層位渦收支分析初探;The feasibility of using the constancy of rank distribution for climate projections and the preliminary study of layered potential vorticity budget analysis
    Authors: 戴世忠;Tai, Shih-Chung
    Contributors: 大氣科學學系
    Keywords: 秩等級分布;完美模式法;秩等級直方圖修正法;層位渦;位渦收支;rank distribution;perfect model approach;rank histogram calibration method;layered potential vorticity;potential vorticity budget
    Date: 2020-08-20
    Issue Date: 2020-09-02 14:55:50 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本文涉及兩個主要的研究課題:第一部分中,探討了將一個已知多模式系集(multi model ensemble, MME)秩等級分布(rank distribution)的恆常性作為emergent constraint,以針對相應的未來預測進行偏差校正的可行性。首先,吾人應用「完美模式法(perfect model approach)」來評估一個已知多模式系集的秩等級分布是否和此約束一致。結果顯示,CMIP5 RCP 8.5情境下MME的全球地表平均溫度、地表溫度以及全球多數格點上的降水場均與此約束一致。接著,採用排序修正法(the rank histogram calibration method)來修正上述量場的預測偏差。此法有效地將21世紀末全球地表平均溫度的不確定範圍減少了一半。就地表溫度而言,2081至2100期間的平均MME中位數經修正後,相較於原始的MME中位數呈現出更加平滑與均質的空間變異。更有趣的是,修正後之2081至2100平均降水的MME中位數完全地排除了長期存在的雙間熱帶輻合區偏差。這些結果顯示,此處所提出結合emergent constraint與排序修正的處理步驟有能力針對地表溫度以及降水產生更為精確且可靠的預測。更加重要的是,因為秩等級分布約束的恆常性並不依賴氣候模式未來變化以及當前狀態之間的線性統計關係,所以較先前經驗證並提出的emergent constraint而言,我們可以預期這個方法具備更廣泛的適用性。
    為了檢驗其他動力變量應用於氣候預測評估的可行性,在本文的第二部分中,吾人將先嘗試利用層位渦(layered potential vorticity, LPV)來了解它能否掌握綜觀尺度系統的特徵。由於中緯度系統的層位渦分析在前人的研究中已有所著墨,並獲致正面的結果,我們將著重於熱帶地區的探討,並選取2015年的強烈颱風蘇迪勒(typhoon Soudelor)作為代表個案,實施層位渦的收支分析。研究結果證實,相較於將大氣切分為兩層的分析結果而言,由整層對流層所計算出來的層位渦收支分項能更清楚地凸顯控制方程式中顯著影響因子的效應;另一方面,不管在颱風的增強或減弱階段,層位渦的平流項均主導著系統的發展。非絕熱效應、摩擦效應、垂直傳送與紊流渦度通量輻合等因子對於局部的層位渦趨勢並不具備決定性的影響。
    ;There are two parts involved in the following work. In the first one, we explored the feasibility of using the constancy of rank distribution of a given multi model ensemble (MME) as an emergent constraint to calibrate the corresponding future projections. We first applied the perfect model approach to evaluate whether the rank distribution of a given MME is consistent with the constraint. Results show that the global mean surface temperature (GMST) as well as the surface temperature and the precipitation fields at most grids on the global from the CMIP5 RCP 8.5 scenario MME are consistent with the constraint. We then applied the rank histogram calibration method to calibrate future projections of these fields. For the GMST, we successfully narrow the 5-95 uncertainty range by one half at the end of the 21st century. For the surface temperature field, the calibrated MME medians averaged over 2081-2100 exhibit more smooth and homogeneous spatial variations than those original MME medians. More interestingly, the calibrated MME medians of precipitation field averaged over 2081-2100 are completely free from the long-standing double ITCZ bias. These results suggest that the proposed emergent constraint together with the rank histogram calibration procedure is capable of yielding sharper and more reliable future projections for both the surface temperature and the precipitation fields. More importantly, because the constancy of rank distribution constraint does not depend on linear statistic relations between future changes and current states of climate models, one expects that it has wider range of applicability than previously identified and proposed emergent constraints.
    In order to assess the applicability of another dynamic variable for climate projection evaluations, the layered potential vorticity (LPV) was exploited to understand if it could grasp the characteristics of synoptic scale systems at firsthand in the second part of this dissertation. The budget patterns of Typhoon Soudelor in 2015, which stands for the representatively remarkable tropical system, was then focused on since the mid-latitudinal study had been done in the previous investigation.
    It is validated that the LPV budgets analysis deduced from the entire level of troposphere could present the significant affecting term in the governing equation more clearly, comparing to the multi-layer analyses. The LPV advection effect dominates the whole course of the system development no matter in the strengthening or in the declining period. The synthetic influence from diabatic effect, frictional force, vertical transport and eddy vorticity flux convergent doesn’t show a robust impact for the local LPV tendency.
    Appears in Collections:[大氣物理研究所 ] 博碩士論文

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