Ryder Fox, University of Miami, RSMAS

Photo of Ryder Fox

The grid sizes (>1 km) required for running regional numerical forecasting models operationally means the inability to resolve cloud particles (<1 mm). In order to promote greater computational efficiency, this means that microphysics schemes are used to parameterize, rather than represent individual water species. In the development of each different microphysics scheme, assumptions are made about particle sizes and distributions. While such assumptions increase computational efficiency, uncertainties remain about the dependency of hurricane structure and intensity on particle interactions. To tease out the relationships between ice-phase microphysics and hurricane intensity, this research evaluates six idealized hurricanes initialized with three different microphysics schemes. Vortices were initialized to be either weakly (Category 3) or strongly (Category 5) organized, though otherwise only the microphysics was varied among individual cases. Preliminary analysis shows that while the timing of storm genesis and peak intensity was generally the same among all cases, the Category 3 storms experienced a greater spread of peak intensities than did the Category 5. In cases where the microphysics schemes predicted more ice and snow, the storm widths tended to be broader, with lower altitude light-to-moderate rain. Conversely, storms with more similar distributions of graupel, ice and snow were smaller in size and experienced greater outflow areas. Continued investigations will apply the Brookhaven National Laboratory’s CR-SIM radar simulator to analyze individual species and seek to determine statistical correlations to idealized hurricane intensities.

Abstract Author(s): K. Ryder Fox