Buoyancy Streams and Cloud Flare-Ups Along Rainbands in the Eye Wall of Rapidly Intensifying Storms

摘要

This study addresses the passage of buoyancy streams within moist air along with the rain bands of a hurricane, Ingrid of September 2013 and Gabrielle of August 2013. Moist air along the rain bands of a hurricane supplies buoyancy to the eyewall where clouds grow during the hurricane's intensifying phase. In order to visualize these buoyancy streams, it was necessary to invoke rain rate initialization referred to as Physical initialization for the model. For Ingrid, physical initialization resulted in a relatively moist boundary layer where the buoyancy stream passages were also noted. It was also noted that the convergence of flux of buoyancy contributes to the confinement of buoyancy elements within the moist stream. Physical initialization provided an improvement for the boundary layer moisture along with the rain bands. In Ingrid, the initial moisture analysis (data assimilation) was a little too dry and was improved by invoking physical initialization that made the boundary layer moist. Computations showed a larger population (area occupied) of the buoyant elements before and after physical initialization. This study's salient aspect relates to a time history of buoyancy over a box where the rain band meets the eyewall of hurricane Ingrid. As many as 5-peaks showing buoyancy flare-ups and vertical stretching were followed with increased storm intensification. Monitoring the time history of buoyant elements and their budget is remarkable in the understanding of growing versus decaying phases of these storms.