Convection Scale Based on the Structure of Quasi-Linear Convective Systems from the Perspective of the Grid Spacing of a Meteorological Model

In this study, we aim to investigate the differences between two cases in the dominant convective scales of quasi-linear convective systems (QLCSs) and in the model resolutions required to represent them appropriately. Two QLCS events that occurred in the Kansai region were simulated using multiple horizontal resolutions. One case corresponded to the back building (BB) type, which typically forms under weak vertical wind shear, whereas the other corresponded to the back and side building (BSB) type, which forms under strong shear. Variations in the number of convective cores and vertical momentum transport with resolution were evaluated by classifying convective cores in accordance with their spatial scale. The dominant effective radius of convective cores was 1–4 km in the BB case and 0.5–2 km in the BSB case. This difference reflects the presence of large-scale low-level convergence associated with strong horizontal shear in the BB case, which was absent in the BSB case. These results indicate that the dominant spatial scales of convection are larger in the BB case and smaller in the BSB case, and that a higher model resolution to adequately represent convection is required in BSB-type QLCSs than in BB-type systems.