Comprehensive Evaluations of Mesoscale Convective Systems Simulated in
Convection-permitting WRF Model during the MC3E Field Experiment
Abstract
Mesoscale convective systems (MCSs) are an important component of our
hydrologic cycle as they produce prolific rainfall in the tropics and
mid-latitudes. Recent advancements in high-resolution modeling show
promise in representing MCSs in regional climate simulations. However,
how well do these models represent the complex interactions between
convective dynamics and microphysics in MCSs remain unknown. In this
study, we take advantage of observations collected during the
Midlatitude Continental Convective Cloud (MC3E) experiment to evaluate
multi-scale aspects of MCSs in convection-permitting WRF model. We
conducted three sets of month-long simulations with Morrison and P3
(1-ice and 2-ice categories) microphysics, respectively, at 1.8 km
grid-spacing over the Southern Great Plains. MCSs in observations and
simulations were tracked using a newly developed FLEXTRKR algorithm.
About 15-20 MCSs were identified in the simulations, consistent with
observations. All three simulations underestimate observed monthly total
precipitation which are primarily from MCSs, suggesting the biases might
be caused by large-scale forcings rather than microphysics. All
simulated MCSs overestimate convective area and precipitation amount but
underestimate stratiform rain area and precipitation. Simulated MCS
convective updraft intensities are comparable with radar retrievals for
moderate depths of convective cores, but are too strong for deep cores.
The two P3 simulations have smaller mean ice mass aloft but more
frequent heavy convective rain rate at the surface than the simulation
with Morrison, agreeing better with observations (Figure 1). Simulated
stratiform area ice mass in the upper troposphere are generally larger
than radar retrievals, but the P3 2-ice category has relatively smaller
bias. We will also use polarimetric radar 3-D rain water retrieval to
further evaluate the vertical evolution of rainfall to explain
differences in simulated surface precipitation.