Environmental impacts on tropical cyclone structure and intensity diagnosed from airborne Doppler radar composites

The success of a recent study compositing tropical cyclone (TC) axisymmetric structure derived from airborne Doppler radar measurements has motivated an extension of the analysis to the asymmetric structure. In particular, we examine asymmetry forced by the TC's motion and interaction with vertical wind shear. The compositing method focuses on the core region, and thus scales analyses according to the radius of maximum tangential wind. To the extent that the asymmetries forced by motion and vertical wind shear have a component that is quasi-steady with a preferred azimuthal orientation, compositing relative to the direction of motion and vertical wind shear should yield basic structural properties of translating, sheared TCs. Our analysis begins with a brief examination of this underlying assumption.

To assess the impacts of motion and shear on the core-region asymmetry, we first generate sub-composites based on the relative orientation of the motion and shear vectors using a method similar to Corbosiero and Molinari (2003). We revisit their results using the full kinematic and reflectivity fields offered by the airborne Doppler radar database of at least 77 distinct intensive observation periods. The composited 3-d shear-relative vortex structure is then compared with that in recent theoretical and numerical treatments, and relevant observation-based case studies. Plans to use the composite analysis in the context of HFIP diagnostic efforts and future testing of shear-induced intensity change theories will also be discussed as time permits.