The power dissipation index (PDI), which is defined as the sum of the cube of tropical cyclone (TC) maximum wind speed during TC lifetime, is widely used to estimate the TC destructive potential. However, due to the lack of high-resolution observations, little attention has been paid to the contribution of TC size change to TC destructive potential in response to ocean warming. In this study, sensitivity experiments are performed by using the high-resolution Weather Research and Forecasting (WRF) model to investigate the responses of TC size and TC destructive potential to prescribed sea surface temperature (SST) increase under the present climate condition. The results show that TC size increases with the ocean warming. Possible reasons for TC size change are investigated with a focus on the outer air-sea moisture difference (ASMD). As SST increases, ASMD in the outer zone of the TC is larger than that in the inner zone, which increases the surface entropy flux (SEF) of the outer zone. This change in the radial distribution of SEF causes the increase of tangential wind in the outer zone, which further increases SEF, resulting in a positive feedback between outer-zone SEF and outer-zone tangential wind. This feedback leads to the increase of the radius of gale-force wind, leading to the expansion of TC size. Moreover, to estimate the contribution of TC size change to TC destructiveness, we calculate TC size-dependent destructive potential (PDS) as the storm size information is available in the model outputs, as well as PDI that does not consider the effect of TC size change. We find that PDS increases exponentially as SST increases from 1 to 4°C, while PDI increases linearly; hence the former is soon much greater than the latter. This suggests that the growth effect of TC size cannot be ignored in estimating destructiveness under ocean warming.

中文翻译：

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海洋变暖下的热带气旋大小变化及热带气旋破坏性的相关响应：理想化实验

功耗指数（PDI）定义为TC寿命期间热带气旋（TC）最大风速的三次方之和，被广泛用于估算TC的破坏潜力。然而，由于缺乏高分辨率观测，响应海洋变暖，TC尺寸变化对TC破坏力的贡献很少引起关注。在这项研究中，通过使用高分辨率天气研究和预报（WRF）模型进行敏感性实验，以研究在当前气候条件下TC大小和TC破坏势对规定海表温度（SST）升高的响应。结果表明，TC的大小随着海洋变暖而增加。着重研究了TC尺寸变化的可能原因，重点是外部空气-海洋水分差（ASMD）。随着SST的增加，TC外部区域中的ASMD大于内部区域中的ASMD，这会增加外部区域的表面熵通量（SEF）。SEF径向分布的这种变化会导致外部区域的切向风增加，从而进一步增加SEF，从而导致外部区域SEF与外部区域切向风之间产生正反馈。这种反馈导致烈风的半径增加，从而导致TC尺寸的扩大。此外，为了估计TC大小变化对TC破坏性的贡献，我们在模型输出中可获得风暴大小信息时计算了TC大小相关的破坏性电势（PDS），以及不考虑TC大小影响的PDI更改。我们发现，随着SST从1°C升高到4°C，PDS呈指数增长，而PDI呈线性增长。因此，前者很快就会比后者大得多。这表明在估算海洋变暖下的破坏性时，不可忽视TC大小的增长效应。