P2H.6 Microphysical and dynamical characteristics in the stratiform region of Tropical Storm Gabrielle at landfall

Studying the dynamics and microphysics in stratiform regions of tropical storms is significant due to their contribution to total water budget (i.e. condensation and evaporation) (Gamache et al. 1993) since stratiform precipitation accounts for a relatively large fraction of tropical precipitation. As a significant component of deep stratiform structures, the melting layer has been investigated in many observational and numerical studies (Drummond et al. 1996; Fabry and Zawadzki 1995; Huggel et al. 1996; Srivastava 1987; Willis and Heymsfield 1989; Zawadzki et al. 2005). Willis and Heymsfield (1989) noted that the 0C isothermal layer formed by melting-driven cooling acts like a transition layer that separates dynamics above and below the melting layer. The meltingdriven cooling, concentrated in a narrow melting zone, is more significant in producing mesoscale downdrafts than evaporative cooling from raindrops (Srivastava 1987). As most critical to dynamical and microphysical properties within stratiform precipitation, vertical air motion and horizontal divergence are acquired by using the single-Doppler radar techniques such as VAD (Velocity Azimuth Display) (Browning and Wexler 1968) and EVAD (the extended VAD) (Srivastava et al. 1986; Matejka and Srivastava 1991). Melting-driven cooling can affect the change in bright band intensity and height, depending on precipitation content as well as aggregation degree near the top of the melting layer. The vertical variations in raindrop size distributions (RSDs) below the melting layer are closely linked to the bright band characteristics above. In this study, we utilize the EVAD, the quasiVAD technique (Q-VAD), and the divergence theorem, and also perform the RSD retrievals and a quantitative parameter analysis in order to understand the melting layer dynamics and microphysics in the stratiform region of Gabrielle.