%0 Journal article
%A Hirt, Mirjam
%A Craig, George C.
%A Schäfer, Sophia A. K.
%A Savre, Julien
%A Heinze, Rieke
%T Cold-pool-driven convective initiation: using causal graph analysis to determine what convection-permitting models are missing
%R 10.1002/qj.3788
%R 10.23689/fidgeo-4529
%J Quarterly Journal of the Royal Meteorological Society
%V 146
%N 730

%X Cold-pool-driven convective initiation is investigated in high-resolution, convection-permitting simulations with a focus on the diurnal cycle and organization of convection and the sensitivity to grid size. Simulations of four different days over Germany were performed using the ICON-LEM model with grid sizes from 156 to 625 m. In these simulations, we identify cold pools, cold-pool boundaries and initiated convection. Convection is triggered much more efficiently in the vicinity of cold pools than in other regions and can provide as much as 50% of total convective initiation, in particular in the late afternoon. By comparing different model resolutions, we find that cold pools are more frequent, smaller and less intense in lower-resolution simulations. Furthermore, their gust fronts are weaker and less likely to trigger new convection. To identify how model resolution affects this triggering probability, we use a linear causal graph analysis. In doing so, we postulate a graph structure with potential causal pathways and then apply multi-linear regression accordingly. We find a dominant, systematic effect: reducing grid sizes directly reduces upward mass flux at the gust front, which causes weaker triggering probabilities. These findings are expected to be even more relevant for km-scale, numerical weather prediction models. We thus expect that a better representation of cold-pool-driven convective initiation will improve forecasts of convective precipitation.
%U http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/8875
%~  FID GEO-LEO e-docs