Regional climate model projections of rainfall from U.S. landfalling tropical cyclones
Regional climate model projections of rainfall from U.S. landfalling tropical cyclones
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DOI：
10.1007/s00382-015-2544-y
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发表时间：
2015-03
期刊：
影响因子：
4.6
通讯作者：
D. Wright;T. Knutson;J. Smith
中科院分区：
文献类型：
--
作者：
D. Wright;T. Knutson;J. Smith
美国东部容易受到热带气旋降雨造成的洪水的影响。了解这种降雨的频率和强度在未来气候中将如何变化是一个重大挑战。一个有希望的方法是使用高分辨率区域气候模式对相对粗糙的大气环流模式结果进行动力学降尺度。在本文中，我们研究了登陆的热带气旋的频率和相关的降雨特性在美国东部使用Zetac，一个18公里分辨率的RCM设计用于模拟大西洋热带气旋活动。模拟1980 - 2006年热带气旋频率和降雨强度的8月至10月的比较，从以前的研究和观测数据集的结果。然后将1980 - 2006年的控制模拟结果与三种未来气候情景的结果进行比较：CMIP 3/A1 B（世纪后期）和CMIP 5/RCP 4.5（世纪早期和晚期）。在CMIP 5对世纪早期和晚期的预测中，登陆后的热带气旋在美国东部大部分地区的出现频率几乎没有净变化，尽管海洋上的频率有所下降。这反映了CMIP5预测中更大的登陆比例，这在基于CMIP3的预测中没有看到。在未来的气候预测中，风暴中心500公里范围内陆地上的平均热带气旋降雨率相对于对照增加了8 - 17%。这至少与克劳修斯-克拉珀龙关系所预期的一样多，克劳修斯-克拉珀龙关系将更温暖的大气与更大的大气水蒸气含量联系起来。在陆地上，在较温暖的气候中，给定热带气旋的面积平均降雨率增加百分比在平均半径较大（300 - 500公里）时比风暴附近更大，特别是CMIP 3预测。虽然这项研究并不侧重于归因，但研究结果与最近一项观测研究中记录的历史热带气旋降雨量变化大致一致。这些结果可能对未来热带气旋的洪水风险具有重要意义。
The eastern United States is vulnerable to flooding from tropical cyclone rainfall. Understanding how both the frequency and intensity of this rainfall will change in the future climate is a major challenge. One promising approach is the dynamical downscaling of relatively coarse general circulation model results using higher-resolution regional climate models (RCMs). In this paper, we examine the frequency of landfalling tropical cyclones and associated rainfall properties over the eastern United States using Zetac, an 18-km resolution RCM designed for modeling Atlantic tropical cyclone activity. Simulations of 1980–2006 tropical cyclone frequency and rainfall intensity for the months of August–October are compared against results from previous studies and observation-based datasets. The 1980–2006 control simulations are then compared against results from three future climate scenarios: CMIP3/A1B (late twenty-first century) and CMIP5/RCP4.5 (early and late twenty-first century). In CMIP5 early and late twenty-first century projections, the frequency of occurrence of post-landfall tropical cyclones shows little net change over much of the eastern U.S. despite a decrease in frequency over the ocean. This reflects a greater landfalling fraction in CMIP5 projections, which is not seen in CMIP3-based projections. Average tropical cyclone rain rates over land within 500 km of the storm center increase by 8–17 % in the future climate projections relative to control. This is at least as much as expected from the Clausius–Clapeyron relation, which links a warmer atmosphere to greater atmospheric water vapor content. Over land, the percent enhancement of area-averaged rain rates from a given tropical cyclone in the warmer climate is greater for larger averaging radius (300–500 km) than near the storm, particularly for the CMIP3 projections. Although this study does not focus on attribution, the findings are broadly consistent with historical tropical cyclone rainfall changes documented in a recent observational study. The results may have important implications for future flood risks from tropical cyclones.