利用高解析度大氣模式與CMIP6高解析度氣候模式探討TC頻率與破壞性之現今模擬與未來變化
No Thumbnail Available
Date
2023
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
本研究利用高解析度大氣與海氣模式，系統性評估模式模擬西北太平洋TC (Tropical Cyclone)活動之表現，及推估未來溫室氣體濃度為CMIP5(Coupled Model Intercomparison Project 5)中的RCP8.5 (Representative Concentration Pathways 8.5)與CMIP6中的SSP5-8.5 (Shared Socioeconomic Pathways 5-8.5)暖化情境下，近未來(2021-2050)與21世紀末(2075-2099)西北太平洋TC活動及登陸東亞沿岸地區之變化，並利用GPI(Genesis Potential Index)與SSE (synoptic-scale eddy)能量診斷等工具，分析TC變化機制。結果顯示25~50公里高解析度大氣與海氣模式均可以模擬現今氣候TC生成與軌跡頻率。然而，模式仍低估TC平均最大強度及強烈TC數目，其中海氣模式更低估TC強度。經由SSE能量診斷分析，顯示ISO(Intraseasonal Oscillation)與SSE尺度交互作用，在TC強度增強過程中，扮演重要的角色。海氣模式模擬ISO提供顯著較少的能量給TC發展。ISO南側較弱的水氣通量，較不利TC潛熱釋放，TC可用位能轉換成較少的TC動能，限制TC強度發展。高解析度氣候模式有助於TC活動模擬表現。高解析度海氣(大氣)模式推估在CMIP6 SSP5-8.5 (CMIP5 RCP8.5) 暖化情境下，近未來(2021-2050) (21世紀末(2075-2099))的TC生成數目減少4.3%(50%)，強度增強0.8%(14%)，及伴隨降雨增加5.8%(35.4%)。TC登陸東亞沿岸地區的頻率減少4.5%(51.9%)。暖化效應影響下，高解析度海氣與大氣模式推估近未來與21世紀末西北太平洋TC活動的變化趨勢一致，但變化幅度仍具有不確定性。經由GPI與SSE能量診斷分析，發現高解析度大氣模式推估在21世紀末TC主要生成位置上，中層大氣較乾燥，季風槽減弱伴隨中層下沉運動異常及SSE活動減弱，限制TC生成。然而，在21世紀末，較暖海溫與較弱垂直風切，及SSE動能產生效率增加，有利TC更快速的增強，更具有破壞性。
In this study, we adopted multiple high-resolution (25–50 km) atmospheric and coupled models to systematically investigate the tropical cyclone (TC) activity over the western North Pacific (WNP). We examined the TC activity for the present day and the future under Coupled Model Intercomparison Project 5 (CMIP5) Representative Concentration Pathways 8.5 scenario for the period 2075–2099, and CMIP6 Shared Socioeconomic Pathways 5–8.5 scenario during 2021–2050. The results show that both atmospheric and coupled models can capture TC genesis and trackfrequencies, although the models underestimated the TC intensity and intense TC frequency. The diagnosis of the synoptic-scale eddy (SSE) energetics suggests that the scale interaction between the intraseasonal oscillation (ISO) and SSE plays an important role in the development of the TC intensity during the intensification process. The coupled models underestimated kinetic energy conversion from ISO to SSE.High-resolution coupled (atmospheric) models projected that the TC genesis frequency will decrease by 4.3% (50%), whereas the TC intensity and precipitation will increase by 0.8% (14%) and 5.8% (35.4%), respectively, during the period 2021–2050 (2075–2099) under the CMIP6 SSP5-8.5 (CMIP5 RCP8.5) scenario. The TC landfall frequency over East Asia will decrease by 4.5% (51.9%). Although the trend for projected change in TC activity in the near future in the WNP is consistent with that projected for the end of the 21st century, the magnitude of that change in TC activity remains uncertain under two different periods and scenarios for future warming.The diagnoses of the genesis potential index and SSE energetics suggest that the future reduction in TC genesis frequency during 2075–2099 is mainly attributed to lower, mid-level relative humidity and a weakened SSE perturbation associated with a weakened monsoon trough. However, landfall TCs will be more destructive at the end of the 21st century owing to the warmer sea surface temperature, weaker vertical wind shear, and higher SSE kinetic energy generation.
In this study, we adopted multiple high-resolution (25–50 km) atmospheric and coupled models to systematically investigate the tropical cyclone (TC) activity over the western North Pacific (WNP). We examined the TC activity for the present day and the future under Coupled Model Intercomparison Project 5 (CMIP5) Representative Concentration Pathways 8.5 scenario for the period 2075–2099, and CMIP6 Shared Socioeconomic Pathways 5–8.5 scenario during 2021–2050. The results show that both atmospheric and coupled models can capture TC genesis and trackfrequencies, although the models underestimated the TC intensity and intense TC frequency. The diagnosis of the synoptic-scale eddy (SSE) energetics suggests that the scale interaction between the intraseasonal oscillation (ISO) and SSE plays an important role in the development of the TC intensity during the intensification process. The coupled models underestimated kinetic energy conversion from ISO to SSE.High-resolution coupled (atmospheric) models projected that the TC genesis frequency will decrease by 4.3% (50%), whereas the TC intensity and precipitation will increase by 0.8% (14%) and 5.8% (35.4%), respectively, during the period 2021–2050 (2075–2099) under the CMIP6 SSP5-8.5 (CMIP5 RCP8.5) scenario. The TC landfall frequency over East Asia will decrease by 4.5% (51.9%). Although the trend for projected change in TC activity in the near future in the WNP is consistent with that projected for the end of the 21st century, the magnitude of that change in TC activity remains uncertain under two different periods and scenarios for future warming.The diagnoses of the genesis potential index and SSE energetics suggest that the future reduction in TC genesis frequency during 2075–2099 is mainly attributed to lower, mid-level relative humidity and a weakened SSE perturbation associated with a weakened monsoon trough. However, landfall TCs will be more destructive at the end of the 21st century owing to the warmer sea surface temperature, weaker vertical wind shear, and higher SSE kinetic energy generation.
Description
Keywords
熱帶氣旋, 季內震盪, 尺度交互作用, 全球暖化, 高解析度大氣與海氣氣候模式, tropical cyclone, intraseasonal oscillation, scale interaction, global warming, high-resolution atmospheric and coupled model