Object-Based Evaluation of Precipitation Systems in Convection-Permitting Regional Climate Simulation Over Eastern China

Based on an object-based tracking (OT) algorithm, the precipitation systems in the convection-permitting (CP, similar to 4 km) regional climate model (RCM) are evaluated from the Lagrangian viewpoints. The characteristics of precipitation systems over eastern China during 1998-2007 derived from the CP RCM are compared with the satellite-derived precipitation data set CMORPH. It is found that, with the cumulus parameterization switched off and reasonable representation of complex terrain, the precipitation systems in the CP RCM can propagate in the same direction as observation, but CP RCM tends to under-/overpredict the precipitation systems with slow/fast propagation speed. Nevertheless, CP RCM can reasonably capture the average duration and eccentricity of all precipitation systems. The major deficiency in CP RCM is that the simulated precipitation systems are significantly weaker with larger coverage area. Over-/underrepresentation of precipitation systems driven by large-scale circulations/intense thunderstorms in CP RCM leads to wet and dry biases in the total precipitation of the longer-duration (>= 48 hr) and shorter-duration (<48 hr) systems, respectively. It is suggested that assessment of the lifecycles of propagating precipitation systems in the Lagrangian framework is complementary to the traditional point-to-point Eulerian validation method.

Automated summary

Based on an object-based tracking algorithm, the precipitation systems in a high-resolution regional climate model were evaluated. The model can reasonably capture the average duration and eccentricity of precipitation systems, but it tends to underestimate/overestimate their propagation speed and has a weakness in simulating precipitation intensity and coverage.