0302号(鲸鱼)台风降水和水粒子空间分布的三维结构特征

由于缺乏关于台风结构信息的高分辨率资料,即探测台风云系内部结构特征的技术限制,造成了进一步理解台风的动力传送特征的困难.作者用热带测雨卫星(TRMM,Tropical Rainfall Measuring Mission)的测雨雷达(PR,Precipitation Radar)和TRMM微波图像仪(TMI,TRMM Microwave Imager)资料详细研究了"鲸鱼"台风(0302号)于2003年4月16日1105 UTC的降水和降水云系中各种水粒子的三维结构特征.通过分析发现该时刻:(1)台风降水中大部分区域为层性降水(占总降水面积的85.5%),对流性降水占总降水面积的13.1%,但对流性降水的贡献却达到41.8%,所以,虽然对流性降水所占面积比例很少,但是它对总降水量的贡献却很大.(2)60%降水主要集中在距离台风中心100 km以内的区域,约占总降水量的60%.(3)各种水粒子含量随着与台风中心距离的增加而减少.降水云系中水粒子最大含量出现高度与水粒子的种类和与台风中心的距离有关.最后,分析了台风降水和降水云系中三维分布的成因.

3D Structure of Rain and Cloud Hydrometeors for Typhoon Kujira (0302)

Predicting rainfall associated with tropical cyclones is a major challenge.Due to lack of high resolution data on typhoon structure,i.e.the technical limitation of detecting the cloud structure of inner-typhoon,it is difficult to further understand its dynamic transportation characteristics.A number of case studies have shown that the precipitation structures in tropical cyclones are quite complex and vary from case to case.Early radar images revealed that the typhoon cyclone rainfall is usually organized in bands spiraling toward the storm center,commonly referred to as rainbands.In this paper,the case of super Typhoon Kujira(0302) occurring in April 2003 is chosen.It is located over open water to the north of Papua New Guinea,steadily intensified during the period of TRMM observations and reaches a maximum sustaining wind of 67 m/s identified as class 4.The 3D structure of rain and hydrometeors in rain cloud is studied by use of Visible and Infrared Scanner(VIRS),Precipitation Radar(PR) and TRMM Microwave Imager(TMI) data.The rain type is studied by use of PR data 2A23.It is found that the stratiform rain covers 85.5% area and contributes 58.1% rainfall,the convective rain only covers 13.1% area but contributes 41.8% rainfall.Though the convective rain only covers smaller area of typhoon rain,it is important for the typhoon rainfall.At the same time,the average rain rate of convective rain is 19.78 mm/h,but is only 4.22 mm/h for stratiform rain.The former is about 4.7 times of the latter.This ratio is more than the average ratio for stratiform and convective over the tropical sea area(average ratio is 3.3).The mean rainfall distribution is analyzed by using 2B31 data,which is retrieved from combining of PR and TMI products.The mean rainfall distribution is computed using 5-km annulus from the storm center to a 300-km radius.It is found that the rain rate decreases as the distance from the typhoon center increases.It is about 60% rain which comes from the region within 100 km from typhoon center,but the region covers only 40% of the total typhoon rain area.The vertical profiles of rainfall are studied by using 2A25 retrieved from PR data.The stratiform rain reaches its maximum at different heights for the different distances from typhoon center.The maximum of stratiform rain appears at 5 km height in the region within 50 km from typhoon center and 4.5 km height over the other area.The convective rain rate fluctuates under 3.0 km height in the region within 50 km and increases as the height decreases over the other area.The hydrometeor profiles are studied by using 2A12 data,which are produced by combining models and TMI data.Hydrometeors in typhoon rain cloud decreases as the distance from typhoon center increases.The different types of hydrometeors in rain cloud reach their maximum values at different heights.Most rain cloud water is distributed at the heights of 28 km,and reaches its maximum at 5 km.Most cloud ice is located in the region within 100 km from the typhoon center,and reaches its maximum at 14 km height in this region and 7 km height in the other region.The precipitation water reaches its maximum at 2 km height within 100 km from the typhoon center,but the height increases to 4 km in the region 200 km out from center.Most precipitation ice is concentrated above 7 km height.The studies of the different types of rainfall and hydrometeors 3D structure for tropical cyclone should be helpful in improving the tropical cyclones rainfall forecasting.