Boundary Layer Structure of an Explosive Cyclone.

摘要

A detailed analysis of the horizontal boundary layer structure of the warm front of an open ocean explosive cyclone in Intensive Observation Period (IOP) 2 of the Experiment on Rapidly Intensifying Cyclones in the Atlantic (ERICA) is conducted. Data for this study consists of aircraft data averaged over one minute supplimented by satellite and drifting buoy observations. Analysis of surface winds and fluxes was done using the Brown-Liu Marine PBL model. Results show a PBL which differs from that found in typical cyclones, with large latent heat fluxes south of the warm front and with relatively weak sensible heat fluxes about the warm front. Boundary layer stratification was stable north of the warm front and unstable south of the warm front. A mechanism for moist frontogenesis is proposed whereby the destabilizing effects of the latent heat flux enhances frictional convergence along the warm front. These fluxes warm and moisten the cyclone's warm sector, enhancing unstable convection along the warm front and thereby enhancing the vertical motion. This enhanced vertical motion would strengthen the geostrophic deformation of the theta (sub epsilon) gradient and potentially enhance cyclogenesis.