From Groundwater to the Atmosphere: Using RELAMPAGO Observations and Modeling to Understand Changes in the Hydrologic Cycle of Southeastern South America
Some of the world’s deepest and largest convective storms develop in Southeastern South America (SESA), often resulting in flooding. In the first part of this work, we develop a river streamflow hindcast and forecasting framework using RELAMPAGO observations and WRF-Hydro hydrologic modeling. Our results highlight that ensemble hydrologic forecasts with regional atmospheric data assimilation can provide realistic prediction of an extreme streamflow event in the mountainous region of the Sierras de Crdoba.
During the 21st century, Argentina has experienced one of the fastest agricultural expansion rates in the planet as perennial grasses have been replaced by annual crops like soy. In the second part of this work, we use flux tower observations from RELAMPAGO and land-surface modeling to investigate how the land cover affects the sub-surface, surface and atmospheric fluxes of moisture and energy. When compared to perennial alfalfa, the observations over soy show lower evapotranspiration and higher sensible heat. Modeling results indicate that observed increases in streamflow and decreases in water table depth over time are likely linked to the shifts in land cover. Additionally, a 250% increase in Bowen ratio suggests a significant impact on the atmosphere. In the third part of this work, we investigate the impact of large-scale land use change on the regional hydroclimate of SESA. We use high-resolution ensemble coupled WRF simulations to simulate three extreme hydrometeorological events during spring 2018. The simulated mesoscale convective systems were significantly larger and produced heavier precipitation under current land use conditions when compared to an idealized historic land use scenario. This highlights the potential of land use changes to modify organized deep convective storms and extreme precipitation in SESA.
