Effects of microphysical drop size distribution on tornadogenesis in supercell thunderstorms

[1] Idealized simulations of tornadogenesis in supercell storms are performed using a grid of 100 m spacing. The cold pool intensity and low-level storm dynamics are found to be very sensitive to the intercept parameters of rain and hail drop size distributions (DSD). DSDs favoring smaller (larger) hydrometeors result in stronger (weaker) cold pools due to enhanced (reduced) evaporative cooling/melting over a larger (smaller) geographic region. Sustained tornadic circulations of EF2 intensity are produced in two of the simulations with relatively weak cold pools. When the cold pool is strong, the updraft is tilted rearward by the strong, surging gust front, causing a disconnect between low-level circulation centers near gust front and the mid-level mesocyclone. Weaker cold pool cases have strong, sustained, vertical updrafts positioned near and above the low-level circulation centers, providing strong dynamic lifting and vertical stretching to the low-level parcels and favoring tornadogenesis.

[1]  Erik N. Rasmussen,et al.  Precipitation Uncertainty Due to Variations in Precipitation Particle Parameters within a Simple Microphysics Scheme , 2004 .

[2]  Erik N. Rasmussen,et al.  Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations , 2003 .

[3]  William R. Cotton,et al.  Numerical Simulation of a Tornado Vortex , 1995 .

[4]  H. D. Orville,et al.  Bulk Parameterization of the Snow Field in a Cloud Model , 1983 .

[5]  Idealized simulations of aerosol influences on tornadogenesis , 2008 .

[6]  Jidong Gao,et al.  The Advanced Regional Prediction System (ARPS), storm-scale numerical weather prediction and data assimilation , 2003 .

[7]  William R. Cotton,et al.  The Impact of Hail Size on Simulated Supercell Storms , 2004 .

[8]  K. K. Lo,et al.  The Growth of Snow in Winter Storms:. An Airborne Observational Study , 1982 .

[9]  A. Waldvogel,et al.  The N0 Jump of Raindrop Spectra , 1974 .

[10]  Erik N. Rasmussen,et al.  Direct Surface Thermodynamic Observations within the Rear-Flank Downdrafts of Nontornadic and Tornadic Supercells , 2002 .

[11]  Song‐You Hong,et al.  The WRF Single-Moment 6-Class Microphysics Scheme (WSM6) , 2006 .

[12]  Robert B. Wilhelmson,et al.  The Morphology of Several Tornadic Storms on 20 May 1977 , 1981 .

[13]  Robert Davies-Jones,et al.  Can a Descending Rain Curtain in a Supercell Instigate Tornadogenesis Barotropically , 2008 .

[14]  R. Rotunno,et al.  A Theory for Strong, Long-Lived Squall Lines , 1988 .

[15]  Sensitivity of tornadogenesis in very-high-resolution numerical simulations to variations in model microphysical parameters , 2006 .

[16]  Joseph B. Klemp,et al.  DYNAMICS OF TORNADIC THUNDERSTORMS , 1987 .