Simulations of a synoptically forced transition from shallow cumulus to precipitating cumulus congestus

English Abstract:

We explore the factors controlling the transition from shallow cumulus to precipitating cumulus congestus associated with a mid-latitude synoptic system sampled over the ARM SGP (Atmospheric Radiation Measurement Program Southern Great Plains) region during the MC3E field campaign. A wide array of instruments, including the ARM radar suite, documented the spatial distribution and temporal evolution of cloud and precipitation properties over the region. We employ large-eddy simulation (LES) with size-resolving (bin) microphysics to quantify the relative importance of different factors governing the evolution of cloud properties accompanying the transition. The combination of LES forced with the ARM variational analysis product results in a cloud regime transition that occurs several hours too quickly relative to observations obtained from the ARM radar suite. We present results from simulations that incorporate high temporal resolution retrievals from AERI (atmospheric emitted radiance interferometer) and an adjustment of the advective forcings in order to be more consistent with the evolution of the temperature and moisture profiles. The suite of sensitivity simulations will lead to an improved understanding of the mechanisms governing the transition and suggest a pathway to improve simulation performance.