Impact of resolution and air temperature on Large Eddy Simulation of mid-latitude summer time convection. Under open review for Atmospheric Chemistry and Physics. doi: 10.5194/acp-2019-638

Abstract. We analyze life cycles of summer time moist convection of a Large Eddy Simulation (LES) in a limited area setup over Germany. The goal is to assess the ability of the model to represent convective organization in space and time in comparison to radar data, and its sensitivity to daily mean surface air temperature. A continuous period of 36 days in May and June 2016, showing a considerable amount of convective rainfall which covers large parts of the domain on most of the days, is simulated with a grid spacing of 625 m. Using convective organization indices, and a tracking algorithm for convective precipitation events, we find that an LES with 625 m grid spacing tends to underestimate the degree of convective organization, and shows a weaker sensitivity of heavy convective rainfall to temperature as suggested by the radar data. An analysis of three days within this period that are simulated with finer grid spacing of 312 m and 156 m showed, that a grid spacing at the 100 m scale has the potential to improve the simulated diurnal cycles of convection, the mean time evolution of single convective events, and the degree of convective organization.