Wednesday, 9 November 2016
Broadway Rooms (Hilton Portland )
A 24-hour large-eddy simulation (LES) of tropical oceanic deep convection performed in a 205 km x 205 km domain using a 100-m horizontal grid size has revealed many difficult-to-observe features, including the small-scale structure of updrafts, entrainment in updrafts, downdrafts along the periphery of updrafts, the initiation of new convection by gust fronts, the turbulent structure of cold pools, and even signatures of waterspouts. Several low-level vortices of waterspout strength occurred in the simulation. These vortices would presumably manifest themselves as waterspouts at higher resolution. The preferred locations are along gust fronts which produces low-level vorticity due to horizontal shear. This vorticity is then amplified by stretching due to low-level convergence below active cumulus updrafts. The simulation was based on conditions typical of GATE (GARP Atlantic Tropical Experiment) during which several waterspouts were observed. We will present statistics of the waterspout signatures including lifetimes, intensity, and locations relative to gust fronts and updrafts.
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