A Comparison of Observed and Simulated Warm Season MCS Life Cycles in Argentina

Biases in model representation of mesoscale convective systems (MCSs) have the potential to negatively impact weather and climate prediction. It is therefore important to evaluate the accuracy of simulated MCS properties. However, for a given location, MCSs are relatively infrequent and have significant morphological and life cycle variability. Because of these attributes, model evaluation has tended to focus on either high-resolution case studies that are not necessarily representative of all MCSs, or regional climate simulations with many cases but insufficient output to connect rapidly evolving cloud processes to high-resolution measurements. In this study, we aim to improve the shortcomings of previous approaches by running a 6.5-month long, 1800 x 1500 km Weather Research and Forecasting (WRF) simulation with 3-km grid spacing, 80 vertical levels, and targeted, high frequency output over northern Argentina where MCSs are frequently observed. The simulation covers October 15, 2018 to April 30, 2019 when a vast array of measurements were made during the Cloud, Aerosol, and Complex Terrain Interactions (CACTI) and Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaigns.

Observed and modeled MCS events are identified and tracked consistently using 30-minute top-of-atmosphere infrared brightness temperature and surface precipitation over the entire model domain. We compare a number of characteristics of observed and simulated MCSs including their frequency of occurrence, genesis locations, contribution to total precipitation, as well as the mean size, precipitation intensity, and propagation speed as a function of the MCS life cycle. We then compare these MCS statistics to previously published results for tracked MCSs over the United States to determine whether model biases vary geographically and by large-scale environments. Lastly, we begin the process of understanding differences in observed and simulated MCS life cycle statistics by analyzing field campaign and simulated measurements for MCSs that pass over the RELAMPAGO-CACTI-observing region.