Convective Upscale Growth in Central Argentina: Environmental Conditions and the Role of the South American Low-level Jet

Abstract

Convective upscale growth, the processes by which initially discrete convection grows into large, organized mesoscale convective systems (MCS), impacts convective mode which determines the primary severe weather hazard and plays a key role in redistributing water and energy in the atmosphere. Convection near the Sierras de Córdoba (SDC) in central Argentina frequently experiences rapid upscale growth in the presence of complex terrain as well as the South American low-level jet (SALLJ). This upscale growth occurs over shorter distances than for convection over the U.S. Great Plains which allowed for unprecedented observations of rapid upscale growth. We use targeted field campaign observations along with a high-resolution Weather Research and Forecasting (WRF) simulation to describe the environments under which upscale growth occurs and identify environmental differences across multiple scales that influence the growth rate.We show that the WRF simulation produces a reasonable SALLJ and therefore use the simulation to investigate the impact of the SALLJ on the convective environment. We also compare two cases of observed upscale growth with differing rates and degrees of convective organization to document the environmental conditions and produce hypotheses of how meso-synoptic scale features impact the rate of upscale growth. Lastly, we take a broader look, using the many tracked MCSs in the WRF simulation to compare environments of slow and rapid growth and identify parameters that could differentiate the rate of upscale growth.