Influences of the South American Low-Level Jet on the Convective Environment in Central Argentina Using a Convection-Permitting Simulation

Journal Article · 31 January 2024 · Monthly Weather Review

DOI: https://doi.org/10.1175/mwr-d-23-0122.1 · OSTI ID:2310252

Sasaki, Clayton S. ^[1]; Rowe, Angela K. ^[2]; McMurdie, Lynn A. ^[1]; Varble, Adam C.  ^[3]; Zhang, Zhixiao ^[4]

---

1. University of Washington, Seattle, WA (United States)
2. University of Wisconsin, Madison, WI (United States)
3. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
4. University of Utah, Salt Lake City, UT (United States); University of Oxford (United Kingdom)

This study documents the spatial and temporal distribution of the South American low-level jet (SALLJ) and quantifies its impact on the convective environment using a 6.5-month convection-permitting simulation during the Remote Sensing of Electrification, Lightning, And Mesoscale/Microscale Processes with Adaptive Ground Observations and Clouds, Aerosols, and Complex Terrain Interactions (RELAMPAGO-CACTI) campaigns. Overall, the simulation reproduces the observed SALLJ characteristics in central Argentina near the Sierras de Córdoba (SDC), a focal point for terrain-focused upscale growth. SALLJs most frequently occur in the summer with maxima to the northwest and east of the SDC and minima over the higher terrain. The shallower SALLJs (<1750 m) have a strong overnight skew, while the elevated jets are more equally spread throughout the day. SALLJ periods often have higher amounts of low-level moisture and instability compared to non-SALLJ periods, with these impacts increasing over time when the SALLJ is present and decreasing afterward. The SALLJ may enhance low-level wind shear magnitudes (particularly when accounting for the jet height); however, enhancement is somewhat limited due to the presence of speed shear in most situations. SALLJ periods are associated with low-level directional shear favorable for organized convection and an orientation of cloud-layer wind shear parallel to the terrain, which could favor upscale growth. A case study is shown in which the SALLJ influenced both the magnitude and direction of wind shear concurrent with convective upscale growth near the SDC. This study highlights the complex relationship between the SALLJ and its impacts during periods of widespread convection.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); ARM Data Center, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)
• Grant/Contract Number: AC05-76RL01830; AC02-05CH11231
• OSTI ID: 2310252
• Report Number(s): PNNL--SA-190051
• Journal Information: Monthly Weather Review, Journal Name: Monthly Weather Review Journal Issue: 2 Vol. 152; ISSN 0027-0644
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English