Numerical simulations of the July 10 Stratospheric-Tropospheric Experiment: Radiation, Aerosols, and Ozone/Deep Convection Experiment convective system: Kinematics and transport

The observed July 10, 1996, Stratospheric-Tropospheric Experiment: Radiatio n, Aerosols, and Ozone (STERAO) convective system is broadly reproduced in a nonhydrostatic cloud model simulation using an idealized horizontally hom ogeneous sounding and no terrain. System evolution from a multicellular lin e to a supercell, along with line orientation, anvil structure, horizontal wind fields, depth of convection, and derived radar reflectivity, compares well with observations. Simulated passive tracer transport of CO and ozone generally agrees with aircraft measurements and shows a small amount of ent rainment of environmental air in the updrafts, and a small amount of diluti on occurring with transport downwind in the anvil; the entrainment and dilu tion are less pronounced in the supercell stage. The horizontally integrate d vertical flux divergence for CO in the simulation shows a net gain at alm ost all levels above 8 km mean sea level (msl). The rate of increase of CO mass above 8 km varies significantly in time, with a peak at early times, f ollowed by a decline and minimum as the system transitions to a supercell a nd a steady increase as the supercell matures. Trajectory analyses show tha t updrafts in the simulation are ingesting air from a layer spanning from 2 km to 3.5 km msl (from 0.5 to 2 km above the surface). The residence times for parcels in the updraft varies from just under 10 min to more than 20 m in, with most parcels taking approximately 10 min to ascend to the anvil.