Impact of resolution on large-eddy simulation of midlatitude summertime convection

Abstract

We analyze life cycles of summertime 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 d in May and June 2016 is simulated with a grid spacing of 625 m. This period was dominated by convection over large parts of the domain on most of the days. 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 3 d with in this period that are simulated with a finer grid spacing of 312 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.