Evaluation of double-moment representation of warm-rain and ice hydrometeors in bulk microphysical parameterization with numerical simulations and UND-Citation aircraft observations during MC3E

Description

The influence of double-moment representations of warm-rain and ice hydrometeors on the numerical simulations of a Mesoscale Convective System (MCS) over the Southern Great Plains (SGP) during the Midlatitude Continental Convective Clouds Experiment (MC3E) has been investigated. The Weather Research and Forecasting (WRF) model is used to examine the sensitivity of numerical simulations of a MCS to three different microphysical schemes, including the WRF single-moment 6-class (WSM6), WRF double-moment 6-class (WDM6), and Morrison double-moment (MORR) schemes. Simulations are validated with surface Mesonet, the National Centers for Environmental Prediction (NCEP) Stage IV rainfall dataset, Next Generation Radar (NEXRAD), and University of North Dakota (UND)-Citation aircraft observations. A cloud classification algorithm is also applied for evaluating the simulated MCS structures. It is found that the simulated structure, lifecycle, cloud coverage, precipitation, and microphysical properties of the convective systems, as well as their associated cold pools, are sensitive to microphysical schemes. Compared with the NCEP Stage IV rainfall and NEXRAD observations, the WDM6 simulation produces the structure and extent of the MCS very well, while WSM6 produces a less organized convection structure with a shorter lifetime. Both simulations heavily underestimate the precipitation amount and the radar echo top and have unrealistic cloud component ratios. With MORR schemes, the model performs well in predicting the lifetime, cloud coverage, echo top, and precipitation. The differences in the convection properties among the simulations occur mainly because the double-moment representations of warm-rain and ice hydrometeors have a strong influence on convective cloud properties that determine the hydrometeor drag and cold pool characteristics, in terms of intensity, size, and depth. In contrast, the comparison between simulated microphysical properties and UND-Citation observations illustrates that double-moment representations of ice hydrometeors (MORR) do not improve the prediction of the ice hydrometeor properties, suggesting that uncertainties in microphysical schemes could still be a productive area of future research.