Wave CISK and Mesoscale Convective Systems

The basic assumptions of conventional wave-CISK theory are examined against observations of mesoscale organized convective systems. The quasi-equilibrium assumption is disputed and a nonequilibrium model of clouds actively responding to mesoscale low-level mass fluxes in a preexisting conditionally unstable atmosphere is formulated. The growth rates of the most unstable mode exhibit. Evident scale selection over a broad range of mesoscale wavelengths. Reasonable response to variations of external parameters. Strong dependence on the gross features of cloud heating, especially on the elevation of maximum heating, upper tropospheric heating, lower tropospheric cooling, and cooling just above the tropopause. Insensitivity to local variations of cloud heating, i.e., to a redistribution of cloud heating within a relatively thin layer. The structures of the resulting propagating growing waves are comparable with observations of midlatitude mesoscale convective systems. Some insights pertaining to the instability and scale selection of this modified wave-CISK model are given by examining its energetics and by using the concept of wave “overreflection.”