基于气候系统模式FGOALS-g2的热带气旋活动及其影响的动力降尺度模拟

热带气旋是气候模拟关注的重要对象，但是，由于当前的气候系统模式分辨率较低，难以合理再现热带气旋分布特征，因此，动力降尺度就成为一种有效的手段。本文使用区域气候模式RegCM3，对中国科学院大气物理研究所气候系统模式FGOALS-g2的模拟结果进行动力降尺度，基于热带气旋路径追踪法，从热带气旋的路径、强度和降水三个方面，检验了动力降尺度在热带气旋模拟能力上的增值。结果表明，动力降尺度结果大幅提升了热带气旋路径频率的模拟，较之全球模式，其与观测的路径频率分布的空间相关系数从0.57提升至0.74；区域模式模拟的热带气旋强度与观测更为一致，全球模式难以模拟40 m s?1以上风速的热带气旋，区域模式能够模拟风速为60 m s?1的热带气旋；在热带气旋降水方面，降尺度后的热带气旋降水贡献率和平均热带气旋降水强度均有所改善，在西北太平洋区域较之全球模式，区域模式将热带气旋降水贡献率和降水强度提高了10%和4.7 mm d?1。动力降尺度后TC（tropical cyclone）的模拟技巧得到提升的区域为西北太平洋区域，但在中国南海区域，技巧提升的不显著甚至有所下降。关于动力降尺度结果在西北太平洋区域的技巧提升，分析表明能够更好体现CISK（Conditional Instability of the Second Kind）机制是主要原因，区域模式模拟的水汽增多、正涡度增强、上升运动增强而垂直风切变减弱都有显著贡献。

Dynamical Downscaling of Tropical Cyclone and Associated Rainfall Simulations of FGOALS-g2

Tropical cyclone (TC) plays an important role in climate research.However,due to the relatively low model resolution,there remain challenges in simulating the distribution of TC by using global climate models.Dynamical downscaling has been a useful tool for TC research.In this paper,a regional climate model RegCM3 was used to dynamically downscale the historical TC simulation of FGOALS-g2(grid-point version 2 of Flexible Global Ocean-Atmosphere-Land System model),a global climate system model developed by LASG/IAP.A tropical cyclone track detection method was applied to reveal the added value of dynamical downscaling in simulating track distribution,intensity and rainfall of TCs.The result of dynamical downscaling shows distinct improvements in simulating the TC distribution,intensity and associated rainfall.The pattern correlation coefficient of TC track distribution is improved from 0.53 to 0.74 by the regional model.The underestimated TC intensity from FGOALS-g2 simulation is enhanced in RegCM3(Version 3 of the Regional Climate Model) by 20 m s⁻¹.In addition,the total rainfall contribution and intensity are enhanced by 10% and 4.7 mm d⁻¹ in RegCM3 compared to that in the global model over the western North Pacific region.In addition to the influence of increasing model resolution,large-scale variables such as increased moisture,enhanced relative vorticity and ascending motion,and weakened vertical wind shear are responsible for the improvements of TC simulating skill in RegCM3 as a result of better reproduction of CISK (Conditional Instability of the Second Kind) mechanism.