Hurricanes and global warming - Results from downscaling IPCC AR4 simulations
Hurricanes and global warming - Results from downscaling IPCC AR4 simulations
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DOI：
10.1175/bams-89-3-347
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发表时间：
2008-03-01
影响因子：
8
通讯作者：
Williams, John
中科院分区：
文献类型：
--
作者：
Emanuel, Kerry;Sundararajan, Ragoth;Williams, John
热带气旋活动的变化是全球气候变化的潜在后果之一，因此，有相当大的兴趣了解人为气候变化可能如何影响这类风暴。全球气候模型目前被用来估计未来的气候变化，但当前一代模型缺乏解决热带气旋强烈内核所需的水平分辨率。在这里，我们回顾了一种从全球模式的输出推断热带气旋气候学的新技术，将其扩展到预测成因气候学(而不是依赖于历史气候学)，并将其应用于由一套支持最新政府间气候变化专门委员会报告的全球模型模拟的当前和未来气候状态。这项新技术通过使用专门的、以角动量坐标表示的海洋-大气耦合飓风模型来解决水平分辨率问题，该模型以低成本提供了高分辨率的核心。这个模型沿着平流和贝塔模型生成的2000个风暴路径中的每一个运行，而平流和贝塔模型又由来自全球模型的大尺度风驱动。在这种方法的扩展中，路径是通过随机播撒具有弱涡旋的大片热带地区，然后允许强度模型根据大范围环境条件确定它们的存活率来启动的。结果表明，该方法在很大程度上成功地再现了热带气旋在当前气候条件下的季节循环和年际变化，在模拟热带气旋的空间分布方面也取得了一定的成功。当应用于二氧化碳浓度是当前浓度两倍的全球气候模拟时，该方法预测了热带气旋活动的实质性变化和地理转移，但所使用的全球气候模型有很大差异。整个盆地的功率耗散和风暴强度一般都随着全球变暖而增加，但不同的模式和不同的盆地的结果是不同的。风暴频率在南半球和北印度洋减少，在西北太平洋增加，在其他地方是不确定的。结果表明，随着气候变暖，边界层湿熵与对流层中层湿熵之差增大，对热带气旋活动的变化有很大影响。
Changes in tropical cyclone activity are among the more potentially consequential results of global climate change, and it is therefore of considerable interest to understand how anthropogenic climate change may affect such storms. Global climate models are currently used to estimate future climate change, but the current generation of models lacks the horizontal resolution necessary to resolve the intense inner core of tropical cyclones. Here we review a new technique for inferring tropical cyclone climatology from the output of global models, extend it to predict genesis climatologies (rather than relying on historical climatology), and apply it to current and future climate states simulated by a suite of global models developed in support of the most recent Intergovernmental Panel on Climate Change report. This new technique attacks the horizontal resolution problem by using a specialized, coupled ocean-atmosphere hurricane model phrased in angular momentum coordinates, which provide a high resolution of the core at low cost. This model is run along each of 2,000 storm tracks generated using an advection-and-beta model, which is, in turn, driven by large-scale winds derived from the global models. In an extension to this method, tracks are initiated by randomly seeding large areas of the tropics with weak vortices and then allowing the intensity model to determine their survival, based on large-scale environmental conditions. We show that this method is largely successful in reproducing the observed seasonal cycle and interannual variability of tropical cyclones in the present climate, and that it is more modestly successful in simulating their spatial distribution. When applied to simulations of global climate with double the present concentration of carbon dioxide, this method predicts substantial changes and geographic shifts in tropical cyclone activity, but with much variation among the global climate models used. Basinwide power dissipation and storm intensity generally increase with global warming, but the results vary from model to model and from basin to basin. Storm frequency decreases in the Southern Hemisphere and north Indian Ocean, increases in the western North Pacific, and is indeterminate elsewhere. We demonstrate that in these simulations, the change in tropical cyclone activity is greatly influenced by the increasing difference between the moist entropy of the boundary layer and that of the middle troposphere as the climate warms.