Low-Level Jet Influences on the Warm Season Convective Environment in Central Argentina

Deep convection frequently forms in the lee of the Andes, at times growing rapidly upscale and propagating over the plains in Central Argentina. The Sierras de Córdoba (SDC) mountain range is a focal point of these storms with mesoscale organized systems often concurrent with the presence of the South American Low-level Jet (SALLJ). Our past work has characterized the SALLJ using observations from the RELAMPAGO field campaign; however, campaign-based observations are by nature limited in space and time. Using output from a 6-month high-resolution WRF model simulation encompassing the RELAMPAGO domain, we explore how the convective environment changes in the vicinity of the SDC when the SALLJ is present.

Agreeing with past work, we found the SALLJ influences the thermodynamic environment. More specifically, during SALLJ periods, low-level specific humidity and CAPE magnitudes are higher on both the west and east sides of the SDC; however, the impacts of the SALLJ are not instantaneous. The impacts accumulate when the SALLJ is present and linger after the SALLJ disappears, which may help explain widespread convection occurring near the end or just after SALLJ periods in both this model run and observations. Significant differences in the magnitude of vertical wind shear were not found between SALLJ and non-SALLJ periods. Even accounting for the wide variation in SALLJ height did not produce a clear relationship between SALLJ strength and wind shear. This result indicates that there are factors that influence wind shear magnitude beyond the SALLJ. There is evidence, however, that the direction of the wind shear vector is oriented in a more north-south direction during SALLJ periods. This orientation of the wind shear could favor faster rates of upscale growth depending on the orientation of the convection. These statistical results and a case study will be presented to illustrate the complexity of the impact of the SALLJ on the dynamic environment near the SDCs.