西北太平洋热带气旋强度变化的若干特征

THE CHARACTERISTICS OF TROPICAL CYCLONE INTENSITY CHANGE IN WESTERN NORTH PACIFIC

使用NOAA海表温度资料、ECMWF再分析资料和JTWC台风最佳路径数据,对1984—2013年30年西北太平洋热带区域(100°E^180°,0~60°N)内热带气旋(TC)的强度变化特征及其与环境风垂直切变(VWS)、海表温度(SST)、最大风速半径(RMW)的关系作了统计分析,尤其关注TC强度突变。结果表明:(1)在研究区域内,TC样本中35.2%强度稳定,52.8%强度变化缓慢,仅12.0%强度突变,约92.7%的迅速加强TC样本发生在其台风及以上强度等级;(2)2000年以来,TC强度稳定样本减少,强度迅速变化样本增多。5月和9—10月是TC强度突变的高频期;(3)超过12 m/s的环境VWS下TC迅速加强较少,且只有台风及以上强度TC才能在大于12 m/s的VWS下迅速加强;(4)TC加强和迅速加强主要在28.5~30.0℃的SST洋面上发生,在较低SST下仍迅速加强的TC强度等级较高;(5)TC样本的RMW多小于100 km,其中强度突变TC RMW峰值区在20~40 km;(6)加强TC的RMW的24 h变化一般减小,减弱TC的RMW则增大;其中强度突变TC尤其明显,超强台风发生迅速加强时,RMW减小的比率达84.6%,但仍有15.4%比率的RMW增大。

Based on the National Oceanic and Atmospheric Administration （NOAA） optimum interpolation sea surface temperature analysis data, European Centre for Medium-Range Weather Forecasts （ECMWF） ERA-Interiln reanalysis data and Joint Typhoon Warning Center （JTWC） best track data from 1984 to 2013. statistical methods are employed to analyze the intensity change of tropical cyclone （TC） in western North Pacific （100 °E-180 °,0-60 °N） and its relationship with environmental vertical wind shear （VWS）, sea surface temperature （SST） and radius of maximum winds （RMW）, especially for TC with rapid intensity change phenomenon. Results indicated that： （1） 35.2% of the TC intensity stay neutral, and 52.8% change slowly, while only 12.0% come with rapid intensity changing, including rapid intensification （RI） and rapid weakening （RW）. About 92.7% of the RI phenomenon occur in typhoon （TY）, strong typhoon （STY） and super Typhoon （SuperTY） intensity categories; （2） Since 2000, samples of neutral TC decrease, while those of RI increase, and the highest frequency mainly takes place in May, September and October： （3） TCs with VWS over 12 m/s have difficulty in intensifying or RI, except for the strong TCs; beyond Typhoon intensity category; （4） SST between 28.5-30 ℃ is favorable for TC intensifying and RI. While only strong TCs can still intensify rapidly with lower SST; （5） TCs tend to have a RMW smaller than 100 km. TCs with rapid changing intensity tend to be in 20-40 km RMW; （6） 24-hour variation of RMW is reduced tbr the intensifying TCs and enlarged for the weakening TCs, especially for TCs with RI. 84.6% of the RMW in SuperTY with RI phenomenon is reduced, but 15.4% with the R! phenomenon is still enlarged.