环境因子对西北太平洋热带气旋气候特征的影响

The relationship between environmental factors and tropical cyclone activity in the western North Pacific

为研究环境因子对西北太平洋热带气旋气候特征的影响,选取影响热带气旋（TC）活动的4个单向环境因子：海表温度、850 hPa气温、对流层中低层比湿（925~500 hPa）和风速垂直切变（200~850 hPa）,海表温度只表征了海洋的加热状态,而后3个因子则只反映了大气的状态.通过分析这4个环境因子与西北太平洋TC活动的相关关系,进而定义两个指数：考虑海气耦合作用的指数ΔT（ΔT=SST-Ta,其中SST、Ta分别为海表温度和850 hPa气温）以及反映海洋上空湿空气稳定度的指数Δsθe（Δsθe=sθe850-sθe1 000,其中sθe850、sθe1 000分别表示850 hPa、1 000 hPa的假相当位温）.结果表明,指数ΔT以及Δsθe与西北太平洋TC活动的相关性均比较显著,其中考虑了海气耦合作用的指数ΔT能更好地表征TC活动的气候变化.

In order to better understand the relationship between environmental factors and tropical cyclone（TC） activity in the western North Pacific（WNP）.The sea surface temperature（SST）,850 hPa temperature,specific humidity index（between 925~500 hPa） and vertical wind shear（between 200~850 hPa） are chosen over the WNP during a 32-yr period from 1970-2001.All the indices either represent oceanic warming（such as SST）,or only reflect atmospheric conditions.The results show that 850 hPa temperature and specific humidity index both positively contribute to the development of TC activity.Particularly,the SST and vertical wind shear inhibit TC activity.According to the results,two indices are defined.One is the temperature difference between 850 hPa temperature and SST which represents atmosphere-ocean coupling influence.The other reflects static stability between 850 hPa and 1 000 hPa of atmosphere.After analyzing the indices,it is found that,the temperature difference considering the coupling degree of air-sea is of significant impact on TC activity.