A Composite Mesoscale Cumulonimbus Budget.
Atmospheric science paper,
COLORADO STATE UNIV FORT COLLINS DEPT OF ATMOSPHERIC SCIENCE
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Composite maps from 950 mb to 150 mb of relative wind field, mixing ratio r, equivalent potential temperature theta sub E and temperature perturbation for the growth and decay phases of a mean mesoscale cumulonimbus system were constructed using radar and one rawinsonde experiment VIMHEX for days with similar synoptic scale wind field. Mass flows into the mean system give vertical mass transports for growth and decay phases, and net mass balance. The net convergence of r closely balances a mean surface rainfall per echo and the net enthalpy source by the cumulonimbus system. Fluxes of theta sub E into and out of the system for 5 K ranges confirm energy conservation, and give updraft, downdraft transports. The mesoscale transports are related to the large-scale modification of the mean atmosphere using a theoretical cumulonimbus model. The large scale vertical motion is computed as a residual from the temperature and water vapour budgets. Suitably averaged, the large scale and cumulonimbus mass transports are similar but not identical. It is concluded that a parametric model of cumulonimbus convection in terms of mass transport is quite realistic above the surface 150 mb, where the effects of horizontal variations between updraft and downdraft dominate.