Convective Characteristics of Hurricane Eyewalls and Rainbands from 11 years of TRMM Data

To analyze the convective characteristics of hurricanes for different intensity and intensity change stages, we have devised a semi-subjective approach of separating precipitation features of cyclones into the eyewall, inner band, and outer band regions. Our technique employs satellite observations captured by the Tropical Rainfall Measuring Mission (TRMM) since 1998. TRMM orbits are analyzed manually and eyewall and rainband boundaries are documented. Because all orbits are examined individually it is impossible to completely eliminate human interpretation biases. To reduce subjectivity, a detailed, systematic method was implemented to be as consistent as possible. Fixed radii circles are overplotted onto each TRMM overpass image to help the user document eyewall and rainband boundaries for each individual image. Two sets of data are analyzed, one for the TRMM Precipitation Radar (PR) which has a swath width of approximately 250 km, and one for the TRMM Microwave Imager (TMI) which has a swath width exceeding 700km. A total of over 10,000 TRMM orbits are analyzed for over 900 tropical cyclones during 1998-2008. From these unique datasets the convective proxies, as observed by TRMM radar, radiometer, and lightning sensor, of the eyewalls and rainbands can be studied in relation to cyclone intensities and cyclone intensity changes. These properties include the radar reflectivity profile, maximum height of 20 dBZ echo, minimum brightness temperature in IR and passive microwave channels (37 and 85 GHz), and flash rate. Preliminary results indicate that eyewall regions produce the most intense convection followed by the outer rainbands and finally the inner rainbands. The data are used to investigate the relative strength of convection in the eyewalls versus the outer rainbands with respect to storm intensity changes.