The Impact of Topography on the Environment and Life Cycle of Weakly and Strongly Forced MCSs during RELAMPAGO

Journal Article · Thu Sep 01 00:00:00 EDT 2022 · Monthly Weather Review

DOI:https://doi.org/10.1175/mwr-d-22-0049.1· OSTI ID:1980938

Rocque, Marquette N. ^[1]; Rasmussen, Kristen L. ^[1]

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1. Colorado State Univ., Fort Collins, CO (United States)

Intense deep convection and large mesoscale convective systems (MCSs) are known to occur downstream of the Andes in subtropical South America. Deep convection is often focused along the Sierras de Córdoba (SDC) in the afternoon and then rapidly grows upscale and moves to the east overnight. However, how the Andes and SDC impact the life cycle of MCSs under varying synoptic conditions is not well understood. Two sets of terrain-modification experiments using WRF are used to investigate the impact of topography in different synoptic regimes. The first set is run on the 13–14 December 2018 MCS case from RELAMPAGO, which featured a deep synoptic trough, strong lee cyclogenesis near the SDC, an enhanced low-level jet, and rapid upscale growth of an MCS. When the Andes are reduced by 50%, the lee cyclone and low-level jet that develop are weaker than with the full Andes, and the resulting MCS is weak and moves faster to the east. When the SDC are removed, few differences between the environment and resulting MCS relative to the control run are seen. A second set of experiments are run on the 25–26 January 2019 case in which a large MCS developed over the SDC and remained tied there for an extended period under weak synoptic forcing. Finally, the experiment that produces the most similar MCS to the control is when the Andes are reduced by 50% while maintaining the height of the SDC, suggesting the SDC may play a more important role in the MCS life cycle under quiescent synoptic conditions.

• Research Organization: Colorado State Univ., Fort Collins, CO (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC)
• Grant/Contract Number: SC0022056
• Other Award/Contract Number: AGS-1661657; AGS-2146709; 80NSSC21K1618
• OSTI ID: 1980938
• Journal Information: Monthly Weather Review, Journal Name: Monthly Weather Review Journal Issue: 9 Vol. 150; ISSN 0027-0644
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Meteorology & Atmospheric Sciences
South America
mesoscale systems
mountain meteorology
orographic effects
synoptic-scale processes