Basic Convective and Mesoscale Research
Other Agency – The Role of Precipitation on Large Eddy Simulations of Trade Cumulus
Funding Type: Office of Naval Research
Objectives
Employ large eddy simulation with size-resolving microphysics (SAMEX)
to evaluate the role of precipitation in trade cumulus dynamics.
Accomplishments
One of the foci of the RICO (Rain in Cumulus over the Ocean) project
was to evaluate the role of precipitation in the dynamics and evolution
of the trade cumulus boundary layer. The CIMMS cloud physics group
was one of 15 international groups to participate in a model intercomparison
to explore whether state of the art LES models are capable of producing
the characteristic features of trade cumulus as sampled during the
field project. The CIMMS group was one of only three to employ LES
(SAMEX) with a size-resolving microphysical formulation.
Preliminary results from the 24-h intercomparison simulation emphasize overall cloud characteristics. Cloud fraction, for example, fluctuates between 0.1 and 0.2, consistent with the snapshot plan view of albedo. Cloud base is largely dictated by surface thermodynamics and remains relatively steady over the course of the simulation, while maximum cloud top is highly variable and closely tied to the life cycle of individual cumulus towers. The inversion height steadily increases, a result of penetrative entrainment from updrafts rising as far as several hundred meters above the inversion and into the free troposphere.
This project is ongoing.
SAMEX results for the RICO trade cumulus intercomparison. Plan view of albedo at 12 h.