登陆我国内陆热带气旋的衰减趋势分析

Analysis of the decay trend of tropical cyclones landing in China's mainland

全球变暖背景下,登陆热带气旋(Tropical Cyclone,TC)的衰减速度是否放缓存在争议,登陆时强度不同的TC的衰减趋势是否一致还不清楚.利用两个描述登陆TC衰减的物理量,即登陆衰减时间尺度τ和登陆衰减维持时间D,研究了1980-2021年登陆我国内陆TC的衰减变化趋势,并探讨了TC登陆强度分档对衰减变化趋势的影响.对于登陆我国内陆的TC,无论是τ还是D,整体来看都没有随时间显著变化的趋势.进一步将TC的登陆强度分为热带风暴(Tropical Storm,TS)、强热带风暴(Severe Tropical Storm,STS)和台风(Typhoon,TY)档,发现不同强度档的登陆TC,其登陆地点以及登陆后的路径体现出不同特征,使得不同强度档登陆TC的衰减趋势存在差异.从TS档到STS档再到TY档,τ随时间的变化趋势从增加到减小再到明显减小,呈连续改变,而D的变化趋势从增加到减小再到增加,未呈连续改变,表明登陆TC的衰减变化趋势在不同登陆强度条件下存在不一致性.从显著性上看,只有TY档登陆TC的τ的变化满足90%置信区间显著下降趋势,表明登陆TC衰减趋势在不同登陆强度条件下存在不确定性.

In the context of global warming,it is controversial whether the decay of landfalling tropical cyclone(TC)slows down,and it is unclear whether the trend of decay of landfalling TCs with different landing intensity is consistent.In this paper,two physical quantities describing landfall TC decay,decay time scaleτand decay duration D,are used to study the trend of landfall TC decay for TCs landing in China's mainland from 1980 to 2021,and the influence of different landing intensity on the trend is discussed.For all the TCs landing in China's mainland,the trend over time forτor D has no significant change.In this paper,the landfalling TCs are further divided into groups of tropical storm(TS),severe tropical storm(STS)and typhoon(TY)according to their landing intensities.It is found that the landing sites and post-landing paths of the different TC groups show different characteristics,resulting in different decay trends.From TS group to STS group and then to TY group,the trend ofτover time changes continuously from increasing to decreasing to obviously decreasing,while the trend of D changes from increasing to decreasing to increasing,and does not change continuously,indicating that the decay trend is inconsistent for TCs with different landing intensity.From the significance point of view,only the trend ofτof TY group meets the significant decline trend of 90%confidence interval,indicating that the decay trend is uncertain for TCs with different landing intensity.