资源环境科技发展态势分析平台

Dual-polarization radar observations of Hurricane Irma (2017) provide new insight into the microphysical structure of a mature tropical cyclone that can be tied to the cyclone dynamics. The primary eyewall exhibited a radar signature of hydrometeor size sorting, which implied that large drops fell out near persistent upward motion in the front-right quadrant of the storm, while smaller drops were advected downstream. In the outer rainbands, convective initiation was also preferred in the front-right quadrant, whereas stratiform precipitation was predominant downwind. For both the primary eyewall and outer rainbands, the preferred quadrant for convective initiation was consistent with the expected kinematic asymmetry of a tropical cyclone in weak environmental wind shear but with moderate translation speed. The developing secondary eyewall exhibited a different asymmetry that indicated a stratiform-to-convective transition associated with heavy precipitation in the rear quadrants. This transition is consistent with hypothesized dynamical theories for secondary eyewall formation.

Plain Language Summary Understanding the sizes, shapes, and types of precipitating particles in tropical cyclones is important for understanding how tropical cyclones change intensity and structure. This study uses radar observations of Hurricane Irma (2017) to explore these precipitating particles as the storm tracked north of Puerto Rico. We found that the precipitation particles of the primary eyewall, secondary eyewall, and outer rainbands were all distributed asymmetrically around the storm. Their specific distributions were tied to the evolving wind field, and provided new insight to the interconnected physical processes that govern the precipitation features of a tropical cyclone. The results from this study can be used for validating weather models used for tropical cyclone prediction.