ABSTRACT
Temperature inversions often play an important role in severe weather environment. For this reason the COMMAS (COllaborative Model for Multiscale Atmospheric Simulation) cloud model was used to study how thunderstorms are modified upon encountering an inversion. The environment in the model ranges from a buoyand sounding in the weatern region of the domain to an environment in the eastern region containing a capping inversion. A supercell or squall line is generated in the western domain which then propagates eastward into the inversion region. The simulations performed exhibit clear differences in storm structure and evolution for environments with and without inversion layers.
The supercell simulations showed that strong inversions can weaken and destroy a supercell, but a suercell can sustain itself and intensify inside a moderate inversion region. A favorable vertical pressure gradient force in the low levels of the supercell allows it to draw moist air from below the inversion to sustain itself, despite significant negative buoyancy at low levels. The vertical pressure gradient force at mid and low levels was positively correlated with the maximum updraft for the supercells in the moderate and non-inversion cases.
The squall line simulations had more intense convection with increasing inversion strength. All the squall lines survived for the duration of the simulation (5 hours) and had a similar evolution. The shear and outflow induced vorticity at low levels was most closely in balance for the strong inversion case. The low level vorticity balance across the gust front was well correlated with the updraft strength and the vertical orientation of the main updraft.