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.