The detection of flow asymmetries in the tropical cyclone environment

Data from a numerical simulation of a moving barotropic vortex on a sphere with 10-km resolution are used to assess the ability of a state-of-the-art objective analysis scheme to detect certain large-scale tropical cyclone asymmetries, the so-called "beta-gyres' to which the cyclone motion appears to be attributed. It is shown that for a moderate-size tropical cyclone-scale vortex, a regular grid spacing on the order of 100-150 km is required to adequately define the gyres, at least when the ambient flow is weak. The upgraded upper-air network was found to be inadequate by itself for this purpose, suggesting that aircraft dropwindsonde data are a prerequisite for this task. -from Authors