Initiation of deep moist convection over the Sierras de Córdoba mountains in Argentina

Previous studies using satellite and radar data show that some of the most intense convective storms on earth initiate over and near the Sierras de Córdoba (SDC) mountain range in Argentina. One postulated mechanism of convection initiation (CI) over the SDC range is convergence owing to the interaction between the topography and the northerly, warm, moisture-laden South American low-level jet (SALLJ). Significant gaps in knowledge still remain as to how the topography modifies the flow and whether other mesoscale processes contribute significantly to CI. This study aims to explore the contributions of thermally forced daytime upslope flows and SALLJ to low-level convergence and updraft formation, and eventually CI. Numerical simulations of CI over the SDC mountains were conducted using Cloud Model 1 (CM1) at horizontal grid spacings of 250 m and 1 km. The 250 m simulations were large-eddy simulations that used a subgrid-scale turbulence model while the 1 km simulations used Yonsei University PBL scheme. The environmental thermodynamic and wind profiles were taken from IOP4 of the RELAMPAGO-CACTI field campaign. During the IOP4 event, a supercell formed, with CI apparently involving interactions between the topography, SALLJ, upslope flows, and an outflow boundary generated by previous convection. Four numerical simulations of progressively increasing complexity were performed to parse the contribution of uplsope flows, background winds, outflow boundary forcing, and synoptic-scale lift to CI. Preliminary results indicate that model produces CI when the outflow boundary interacts with the heated terrain, as seen in the observations. The model output was compared to data collected during the REMAPAGO-CACTI campaign in terms of flow around the terrain, boundary layer depth, and the vertical profile of static stability turbulent kinetic energy.