西北太平洋迅速增强热带气旋内核区微波亮温特征
首发时间:2018-03-08
摘要:利用美国国防气象卫星专用微波成像仪(SSM/I)和热带测雨卫星微波成像仪(TMI)的85GHz与37GHz微波资料分析了西北太平洋热带气旋(TC)不同强度变化阶段,特别是迅速增强(RI)前后内核区微波亮温的特征。文中根据TC未来24小时的强度变化将TC分为了迅速衰减、慢衰减、成熟、慢增强和迅速增强五个阶段,结果表明,TC内核区中对流活动虽强,但85GHz和37GHz的极化修正温度(PCT)仍是以弱散射信号为主。RI阶段与其他强度变化阶段相比,内核区小于250K的PCT85和小于270K的PCT37主要集中在风切变左侧,其中190-225K的PCT85和260-270K的PCT37 在风切变左右两侧面积的差较为明显。此外,RI发生前内核区190-225K、225-250K的PCT85和260-270K的PCT37的面积分别不超过总内核区的30%、50%和60%,随着RI的发生,亮温集中区域移动至TC中心周围,形态趋于对称。内核区PCT85最小值小于190K和PCT37最小值小于250K的出现频率表明,RI阶段TC内核区强对流的出现频率高于其他强度变化阶段(约71%),且其中大部分均出现在RI发生12小时以前。
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Brightness Temperature Characteristics Of Inner-core In Western North Pacific Rapid Intensify Tropical Cyclone
Abstract:Using passive microwave satellite data from Special Sensor Microwave Imager (SSM/I) and TRMM Microwave Imager (TMI) for Western North Pacific Tropical Cyclone (TC), the brightness temperature characteristics of inner-core were analyzed in different intensity change categories and different intensity change period of Rapid Intensification (RI). In this reaserch, TCs are devided into five intensity categories which are rapid weakening, slow weakening, neutral, slow intensification, and rapid intensification by 24-h intensity changes. The results show that, although the convection in inner-core is strong, the weak scattering signal of 85GHz and 37GHz Polarization Corrected Temperature (PCT) are still the majority. PCT85 below 250K and PCT37 below 270K are mainly located on shear left inner-core regions in rapid intensification TCs comparing with TCs in other intensity change categories, and the difference of 190-225K PCT85 and 260-270K PCT37 area between shear left and shear right in inner-core are obvious. Meanwhile, the 190-225 K, 225-250 K PCT85, and 260-270K PCT37 areas are less than 30%, 50%, and 60% of total inner-core region before RI onset. After RI onset, brightness temperature will be around TC center, forming more symmetrical. The frequency of minimum PCT85 below 190K and minimum PCT37 below 250K inside inner-core indicate that the occurance frequency of strong convection inside inner-core in RI is higher than that of other intensity categories, and most strong convection occurs 12 hours before RI onset.
Keywords: tropical cylone rapid intensification brightness temperature inner-core convection
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西北太平洋迅速增强热带气旋内核区微波亮温特征
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