Shallow Cumulus Cloud-Base Vertical Velocity II: Factors contributing to differences between simulations and observations

 

Authors

Satoshi Endo — Brookhaven National Laboratory
Damao Zhang — Pacific Northwest National Laboratory
Pavlos Kollias — Stony Brook University
Andrew M. Vogelmann — Brookhaven National Laboratory
William I. Gustafson — Pacific Northwest National Laboratory
Katia Lamer — Brookhaven National Laboratory
Heng Xiao — Pacific Northwest National Laboratory
Mariko Oue — Stony Brook University
David Romps — Lawrence Berkeley National Laboratory

Category

Warm low clouds, including aerosol interactions

Description

Large-eddy simulations (LES) conducted by the LES ARM Symbiotic Simulation and Observation (LASSO) project were evaluated using Doppler lidar observations collected at several sites at and around the Atmospheric Radiation Measurement (ARM) Facility Southern Great Plains (SGP) observatory. Initial results suggest that LES significantly underestimates the frequency of occurrence of downdrafts at the cloud base of shallow cumulus clouds (see poster by Vogelmann et al.). The current work attempts to pinpoint the factors responsible for such discrepancies using model sensitivity studies and Observation System Simulation Experiments (OSSEs). The studies start with utilizing LES fields provided by the LASSO project. Sensitivity studies are then conducted using cases and model forcings from the LASSO library with modified model parameters and configurations (e.g., microphysics, wind forcing). OSSEs use the LES fields to determine how sampling criteria and limits could affect the results.