An Online Moisture Tagging Framework for Detrainment of Convective Hydrometeors and Associated Precipitation in Convection-Permitting Models

Abstract

Convective detrainment is an important process in mesoscale convective systems (MCSs) that strongly influence adjacent stratiform clouds and precipitation. However, it remains difficult to quantify convective detrainment in numerical models. In this study, we develop an online convection identification and water vapor tracer (WVT) framework based on the Eulerian WVTs coupled with Weather Research and Forecasting convection-permitting model. Convection is identified using radar reflectivity, and two types of tracers are introduced to track water species and precipitation within convective regions and those detrained from them, which can be distinguished from those newly generated in the stratiform areas. The framework is applied to both an idealized case and a real case. In the idealized simulation, the framework captures the convective detrainment and its associated precipitation during the lifecycle of convective systems featured by rapid evolution in location and structure. In the real case, the framework demonstrates distinct temporal variations in the intensity and area coverage of stratiform precipitation produced by convective detrainment. Both the ice- and liquid-phase detrainments decrease dramatically at the moment when convective precipitation starts to increase, suggesting intensified conversion from cloud to precipitating hydrometeors. After that, the conversion efficiency weakens, which is favorable for the formation of stratiform clouds and precipitation. Overall, this framework provides a useful tool for quantifying the characteristics and impacts of convective detrainment and for evaluating convective parameterization schemes.