热带气旋潜在生成指数的对比分析及其在西北太平洋的改进

A comparison of tropical cyclone Genesis Potential Indices (GPIs) and a modified version for the western North Pacific

本研究评估了现有热带气旋(Tropical Cyclone,TC)潜在生成指数(Genesis Potential Indice,GPI)对北大西洋和西北太平洋热带气旋生成频数(TC Genesis Frequency,TCGF)时空特征的表征能力。结果表明,现阶段使用的GPIs能较好地再现两个海盆TCGF的空间分布和季节循环特征,以及北大西洋TCGF的年际变化,但几乎不能模拟西太平洋TCGF年际时间尺度上的变化。利用美国联合飓风警报中心(Joint Typhoon Warming Center,JTWC)提供的1979—2017年热带气旋最佳路径数据集和ERA-Interim再分析数据,对西北太平洋GPI进行了改进。考虑到相对涡度在西北太平洋对热带气旋生成的重要作用,将绝对涡度分离为相对涡度和地转涡度(f),移除相对湿度,使用多元线性回归的方法构建了GPI WNP。与现有GPIs相比,改进后的GPI WNP不仅对西北太平洋TCGF的空间分布和季节循环有较好的模拟能力,并且可以再现其年际变化特征。

This study evaluates the performance of several existing tropical cyclone(TC)genesis potential indices(GPIs)in reproducing the observed TC genesis frequency(TCGF)in the North Atlantic and western North Pacific(WNP)from 1979 to 2017.The results demonstrate that the existing GPIs can reasonably replicate the climatological distribution,annual cycle,and interannual variability of TCGF in the North Atlantic.However,they fail to reproduce the interannual variability of TCGF in the WNP.To address this limitation,a modified GPI is developed for the WNP,utilizing best-track TC data and ERA-Interim reanalysis data spanning 1979—2017.The modified GPI incorporates earth vorticity(the Coriolis parameter)and relative vorticity separately instead of absolute vorticity and excludes relative humidity,which is commonly used in existing GPIs.Compared with the existing GPIs,the modified GPI can reproduce not only the climatological distribution and annual cycle but also the interannual variability of TCGF in the WNP,particularly in the southeastern region.Additionally,the modified GPI is evaluated using NCEP/NCAR,JRA-55,and ERA5 reanalysis datasets,demonstrating consistent and improved performance in reproducing the interannual variability of TCGF,especially when employing JRA-55 or NCEP/NCAR reanalysis datasets.