The evolution of raindrop size distributions within Hurricane Ike (2008)

Hurricane Ike made landfall in Texas in September of 2008. Using two particle size and velocity (PARSIVEL) optical disdrometers, data were collected on a cross-section through Hurricane Ike at one minute intervals. Data were collected continuously for eighteen hours, allowing us to resolve the raindrop size distribution in the outer and inner rainbands, eyewall and eye of the storm. The drop size distribution parameters (for example, the slopes, intercepts and shape factors of the gamma distributions) for different storm features were derived. When the drop size distributions were compared between the storm's features, very different drop characteristics emerged between the storm's outer rainbands and its inner rainbands and eyewall. This finding has implications for calibrating the reflectivity-rain rate (Z-R) relationship; in short, it suggests that we may need a different Z-R relationship for different parts of a tropical cyclone. The data indicate that rainfall is primarily convective within the hurricane, with small transitional regions. Furthermore, we will investigate the drop size characteristics within dynamical features (for instance, mesoscale vortices and horizontal convective rolls) that occurred during Hurricane Ike.