RELAMPAGO Hydrometeorology Component: Land Surface Controls on Heavy Precipitation and Flooding in the Carcarana River Basin, Argentina

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Hydrometeorological impacts from organized, continental warm season convection are some of the most disastrous and costly of weather-related impacts. Globally, each year, these severe weather events cause intense rainfall, hailstorms, tornadoes, flash floods, and landslides which in turn result in significant crop losses, property damage, urban hazards and loss of human life. Despite the enormous impact such events have on society, the mechanisms driving intense, organized convection and the coupled hydrological responses from those events are not well understood. In this work, we will perform an observational field campaign and coupled modeling study using focused on warm season convection in the Carcarañá River basin in Argentina. The geographical focus on this region stems from the fact that some of the world's deepest and largest convective storms develop at the foothills of the Sierras de Córdoba - a mountain range east of the Andes which is the headwaters of the Carcarañá. Compared to the Great Plains of the United States, convective organization and propagation in subtropical South America is more frequent and confined to a much smaller region - which causes the Carcarañá river basin to be continuously affected by these severe storms, confines the spatial extent of the observational studies and increases the probability of capturing extreme events during a field campaign.The study leverages from and complements the multi-institutional RELAMPAGO/CACTI effort. The observational and modeling work is approached from two perspectives. The first investigates how the land surface impacts the initiation and growth of convective precipitation (atmospheric perspective). The second investigates if changes in land cover have affected the hydrologic cycle and the probability of flooding in the basin (hydrology perspective). The impact of this work is threefold: it addresses fundamental scientific questions in hydrometeorology, drives improvements in fully-coupled hydrometeorological models and ultimately improves predictive skill of high impact weather events.This work combines an integrated hydrometeorological field campaign and coupled modeling study using the WRF/WRF-Hydro system focused on the Carcarañá River basin in Argentina. This basin drains east from the Sierras de Cordoba, a mesoscale mountain range east of the Andes, toward the plains. Frequently impacted by severe, organized convection, the Carcarañá basin is ideally suited to perform observational and modeling studies aimed at understanding the role of the land surface in modulating the observed variability of intense convective systems and associated precipitation and flooding.The overarching science question of this work is: What is the role of the land surface in modulating the observed variability of heavy precipitation and flooding in the Carcarañá River Basin? We address this overarching question with two subsidiary questions: 1. How does land cover heterogeneity (including human-modified land cover) impact initiation and growth of convective precipitation at the local and meso-scale through land-atmosphere exchanges of moisture and energy?2. How have changes in land cover affected the partitioning of rainfall between infiltration/runoff and the residence times of soil moisture and groundwater in the Carcarañá Basin's terrestrial system?The tools we will use are: a) Existing local observations of precipitation, water table depths and streamflow, b) Observations of precipitation, streamflow, soil moisture, temperature and surface fluxes measured by our team during the RELAMPAGO field campaign, c) Numerical simulations using the fully-coupled WRF/WRF-hydro modeling system both in offline mode (i.e. WRF-Hydro only, driven by observed meteorological conditions) and coupled (WRF/WRF-Hydro) modes. Our study region has many similarities with the Great Plains of the United States in terms of the importance of land-atmosphere interactions, the initiation and upscale growth of MCSs and the importance of low-level jet moisture transport. Hence, improved understanding of the hydrometeorology of MCSs will have far-reaching benefits beyond Argentina.