Observations Of Concentric Eyewall Typhoon In The Northwest Pacific Ocean By Multi-sensor

Typhoon accompanied by strong wind, heavy rainfall, storm surge and other natural disasters may be intensified with the global warming. The concentric eyewall is often observed in severe and super typhoon. Spaceborne microwave radiometer provides effective means to observe the concentric eyewall typhoon.In this paper, all the tropical cyclones in the northwest Pacific Ocean from 2002 to 2007 are observed and analyzed statistically by in-orbit microwave radiometers AMSR-E and TMI data combined with CMA-STI and JTWC tropical cyclones dataset. The results indicate that an average of 6 concentric eyewall typhoons occur annually, whose life cycle is 10.6 days while the average life cycle in the northwest Pacific Ocean is 7～8 days; the higher intensity is, the higher possibility is to form a concentric eyewall typhoon, the percentage of concentric eyewall typhoons is 71.4% with Super TY category, 44.4% with STY category and 3.7% with TY category respectively; the formation locations of concentric structure vary with the season in latitude, and they concentrate between 10°N and 20°N in spring and autumn, while concentrate between 20°N and 30°N in summer. This kind of typhoon always occur in the summer.The relationship between the concentric eyewall structure and its intensity and track are discussed. The study suggests that most of the concentric eyewall typhoons become intensified and their growing rates change smoothly before the concentric eyewall structure formation, while they become weak and their decaying rates are close to ordinary typhoon after the formation. Most of the moving tracks are recurving ones, in particularly the mid-recurving track is the most, and the formation points of concentric eyewall structure often appear before the turning points. Taking typhoon 2005-13W-Tailim as an example, this paper shows the evolution of the concentric eyewall sturcture.