The formative processes of clouds have been well understood in studies
of cloud processes. However, the dissipative processes have not received much attentions. In the Tropics, stratiform anvil clouds can last a long period of time after convective parts of mesoscale convective systems cease to be active. This is partly related to 1) that dissipating convective cells merge with stratiform anvils and become of a portion of stratiform anvils and 2) that radiative processes tend to prolong the life cycle of stratiform anvils. In the absence of such physical processes, how long do stratiform anvils last? which mechanism is responsible for the dissipation of stratiform anvils?
In this study, we perform a series of idealized simulations with a cloud-resolving model (CRM). The model starts from a "uniform" sounding, based upon the 4-monthly mean from the TOGA-COARE, with a saturated, moist adiabatic cloud layer above the melting level. The thermodynamic properties of the adjacent cloud-free columns in the two-dimensional CRM satisfy the zero buoyancy condition at every level. A variety of cloud fractions of the initially homogeneous anvil clouds is chosen in the series of simulations. Precipitation and radiative processes are totally neglected. A small amplitude
of large-scale subsidence is imposed in the model. Preliminary analyses of simulations indicate that the anvil clouds can last from 2 h to a few days, depending upon the magnitude of the large-scale subsidence and the horizontal extent and the vertical thickness of the initial anvil clouds. The decaying processes are very complex. The following picture emerges from our preliminary analyses: i) middle portion of cloud subsides and decays more quickly while the edges of cloud rise; 2) the two edges then merge to form a single cloud
at a slightly higher level than the initial cloud (rejuvenating process); 3) the new cloud entity slowly decays at the end.
The parameterization of mesoscale (vertical) transports associated with horizontally inhomogenous stratiform anvils in general circulation models will be eventually addressed.