熱帶氣旋變異度的區域氣候模式模擬分析

Tropical Cyclone Variability Based on Regional Climate Model Simulation

呂易(Yi Lu)

指導教授 ： 吳俊傑

國立臺灣大學/理學院/大氣科學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.03419

摘要

近年來許多研究使用數值模式模擬熱帶氣旋過去的活動和全球暖化假設下的未來投影，但是不同模式間對於熱帶氣旋統計特徵的模擬結果並不一致，存在許多的不確定及敏感性。初始場的擾動對於熱帶氣旋活動的長時間模擬，會使結果產生多大的差異，仍是個有待研究的課題。本研究使用一個高解析度的區域氣候模式(IPRC-RegCM; International Pacific Research Center - Regional Climate Model)，模擬過去二十年(1982-2001)，每年七月至十月的西北太平洋熱帶氣旋的活動，使用NCEP再分析資料及NOAA海表面溫度資料做為模式的邊界條件，並藉由將初始時間提前一天做為系集成員的產生方法，共有四組系集模擬，其初始時間分別為7/1、6/30、6/29、及6/28。
因為初始場的差異，使得四組系集成員對於熱帶氣旋個數的模擬結果有明顯的不同，表示初始擾動在長時間模擬下，對於熱帶氣旋的統計特徵會有顯著的影響。因此計算每年模擬的熱帶氣旋個數之變異數，並藉由合成分析的方式探討極端變異的年份有何大環境特徵。發現在七月至十月的平均大尺度環流場中，變異程度大的年份和變異程度小的年份，其分別的合成分析結果並沒有明顯的環境特徵差異；但是在逐月的合成分析中，可以發現大小變異年的月平均場顯著的不同。整體而言，模式的結果顯示較有利於熱帶氣旋生成的環境場(如較強的低層幅合、較多的水氣等)和較大的垂直風切，會使模式對於熱帶氣旋個數的模擬結果產生較大的變異度。相信藉由這樣的實驗與分析，可以讓我們對於氣候模式與熱帶氣旋統計特徵的模擬之不確定性與敏感性，有更進一步的認識。

關鍵字

熱帶氣旋 ； 變異度 ； 區域氣候模式

並列摘要

A number of studies based on numerical model have been conducted to identify the variations of tropical cyclone activities and their future projections in global warming scenarios. For these studies, the inconsistent responses show the sensitivity and uncertainty on TC statistics in climate models. The issue remains unexplored is how much variability the slightly perturbed initial conditions contribute to statistical TC characteristics in regional climate model. In our study, the high-resolution IPRC (International Pacific Research Center) regional climate model is applied to simulate TC activities in the western North Pacific from 1982 to 2001. The NCEP reanalysis and NOAA OI SST data are used as the boundary conditions to generate four ensemble members, each starting from different initial dates (i.e., 28, 29, 30 June and 1 July).
The large variability of the simulated TC numbers among these four members demonstrates the sensitivity of initial conditions. The variance of TC numbers is calculated, and the years of extreme variance are compared. For JASO mean, our comparison exhibits marked difference of distribution of genesis position between small-variance years and large-variance years but only limited difference in terms of environmental conditions. However, in monthly analysis, favorable conditions of tropical cyclone genesis are found in large-variance years, except for vertical wind shear. It is expected that these results could provide better insights into uncertainty of TC behaviors in numerical models.

並列關鍵字

tropical cyclone ； variability ； regional climate model

參考文獻

Jarvinen, B. R., J. Neumann, and M. A. S. Davis, 1984: A tropical cyclone data tape for the North Atlantic Basin, 1886–1983: Contents, limitations, and uses. NOAA Tech. Memo. NWS NHC, 22, 21 pp.

Dickinson, R. E., A. Henderson-Sellers, and P. J. Kennedy, 1993: Biosphere–atmosphere transfer scheme (BATS) version 1 as coupled to the NCAR Community Climate Model. NCAR Tech. Note NCAR/TN-387+STR, National Center for Atmospheric Research, Boulder, CO, 72 pp.

Bengtsson, L., 1996: Will greenhouse gas-induced warming over the next 50 years lead to higher frequency and greater intensity of hurricanes? Tellus, 48A, 57–73.

Bengtsson, L., K. I. Hodges, M. Esch, N. Keenlyside, L. Kornbleuh, J.-J. Luo, and T. Yamagata, 2007: How may tropical cyclones change in a warmer climate? Tellus, 59A, 539–561.

Bove, M. C., J. O’Brien, J. B. Elsner, C. W. Landsea, and X. Niu, 1998: Effect of El Niño on U.S. landfalling hurricanes, revisited. Bull. Amer. Meteor. Soc., 79, 2477–2482.