应用53 a(1949—2001年)西北太平洋热带气旋(TC)基本资料,分析登陆我国的TC登陆前强度变化的统计特征,包括TC登陆前48 h内强度变化特征、登陆前强度变化的年际、月际和日变化特征、登陆前强度变化与TC自身强度的关系以及TC登陆前的生命史特征等,还对登陆前迅速增强和减弱的TC分布特征进行了分析。主要结果有:(1)随着TC逐渐移向陆地,其强度由增强逐渐转为减弱,转折点大致在登陆前第12 h;(2)TC登陆前平均增强速率为4.0(m/s)/(12 h),标准差为2.9(m/s)/(12 h)。平均减弱速率为-6.2(m/s)/(12 h),标准差为4.8(m/s)/(12 h);(3)TC登陆前的强度变化有明显的年际变化特征,登陆前强度减弱幅度有逐渐减小的趋势;(4)8月TC登陆前强度减弱幅度最小,其次是7月和9月;(5)从日变化看,07时登陆的TC强度变化最明显(-7.2(m/s)/(12 h)),02时最小(-1.5(m/s)/(12 h)),较差达-5.7(m/s)/(12 h);(6)台风登陆前衰减最明显,热带低压减弱幅度最小;(7)登陆前增强TC均在登陆前48 h内持续增强,而且增强速率有逐渐增大的趋势,在登陆前6 h增强幅度显著减小;(8)登陆前增强TC中,登陆华南沿海附近地区(HN)最多,登陆华东沿海及以北地区(HD)最少,登陆台湾岛(TW)的居中;(9)登陆前增强的TC多处在初生不久的发展阶段,而登陆前减弱的TC则多处在维持或衰亡阶段;(10)根据标准差的数学涵义,给出了TC迅速增强和迅速减弱的标准,并对强度突变TC登陆前强度变化与TC强度的关系、登陆前维持时间和区域分布分别进行了简单的分析,给出了一些统计特征。
The statistical characteristics of intensity change in tropical cyclones within 48 hours prior to landfall,as well as their annual,monthly,and diurnal intensity variations were studied.The relationship between intensity change and intensity,life time was analyzed.Furthermore,the spatial distribution of rapid intensifying and filling TCs was obtained.Main conclusions are as follows:(1) 12 hours before landing,these typhoons experience processes from intensifying to filling.(2) On average,the intensifying(filling) rate is 4.0(m/s)/(12 h)(–6.2(m/s)/(12 h)) and the standard deviation is 2.9(m/s)/(12 h)(4.8(m/s)/(12 h)).(3) The ranges of annual intensity variation show decreasing trends.(4) The filling rate in August is the lowest,followed by July and September.(5) On average,these typhoons fill the fastest(slowest) at 07:00(02:00) Beijing Time and the mean filling rate is –7.2m/s/12h(–1.5(m/s)/(12 h)).(6) Among various forms of TCs,i.e.,tropical depression(TD),tropical storm(TS),strong tropical storm(STS),and Typhoon(TY),TY fills the fastest and TD the slowest.(7) These typhoons keey intensifying within the 48 hours before landing,with the amplitude of intensification falling significantly 6 hours before landing.(8) Most of the intensifying TCs land on the south of China and just a small number of them on the east of China.(9) Most of the intensifying(filling) cases of these typhoons are in the stage of developing(maintaining or decaying).