P23 The role of radiation physics in simulating the diurnal cycle of precipitation over the United States using WRF

P.A. Mooney, C.L. Bruyere, National Center for Atmospheric Research, C.J. Broderick*, F.J. Mulligan*, and A. Prein, National University of Ireland Maynooth, Kildare, Ireland

The diurnal cycle of precipitation is an important and fundamental cycle in Earth's climate system. Despite this, climate models struggle to correctly simulate its primary characteristics such as the timing of the peak (phase) and the amplitude of the cycle. It is widely recognised that cumulus schemes strongly influence the model's ability to simulate this aspect of the climate system. However few studies have examined the role of radiation physics in simulating the diurnal cycle of precipitation. In this study, we use the Weather Research and Forecasting model to investigate the influence of radiation physics on WRF's ability to simulate the summertime diurnal cycle of precipitation. For this purpose, we consider the contiguous United States which is a particularly attractive location due the diversity of diurnal cycles and associated physical drivers throughout the region. This is further enhanced by the availability of a high quality data rich observational network. Results show that the radiation schemes influence WRF's ability to the simulate the amplitude of the diurnal cycle but has a negligible impact on the simulation of the timing of maximum precipitation. Through understanding the reasons for this influence, this study adds to our knowledge of the current limitations and capabilities of WRF as a regional climate model, and highlights potential pathways for further enhancing their representation of precipitation dynamics across different spatio-temporal scales.