The Importance of Scale‐Dependent Groundwater Processes in Land‐Atmosphere Interactions Over the Central United States

• Published in: Geophysical research letters 2021-03, Vol.48 (5), p.n/a
• Main Authors: Barlage, Michael, Chen, Fei, Rasmussen, Roy, Zhang, Zhe, Miguez‐Macho, Gonzalo
• Format: Article
• Language: English
• Subjects: dry bias; groundwater; land‐atmosphere interactions; scale‐dependent groundwater processes; warm bias
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL092171

This study explores the impacts of groundwater processes on the simulated land‐surface water balance and hydrometeorology. Observations are compared to multiscale Weather Research and Forecasting (WRF) simulations of three summer seasons: 2012, 2013, and 2014. Results show that a grid spacing of 3 km or smaller is necessary to capture small‐scale river and stream networks and associated shallow water tables, which supplies additional root‐zone water double that of simulations with 9‐km and 27‐km grid spacing and is critical to replenishing the depleted vegetation root zones and leads to 150 mm more evapotranspiration. Including groundwater processes in convection‐permitting models is effective to reduce: (1) 2‐m temperature warm biases from 5–6 to 2–3 °C and (2) the low precipitation bias by half. The additional groundwater supply to active soil flux in convection‐permitting simulations with groundwater for June‐August is nearly translated into the same amount of increased precipitation in the domain investigated. Plain Language Summary Groundwater plays an important role in land‐atmosphere interactions. This study explores the impacts of groundwater processes on the model simulated land‐surface water balance and hydrometeorology. Observations are compared to multiscale Weather Research and Forecasting model simulations of summer seasons for three years: 2012, 2013, and 2014. Results show that high‐resolution modeling (with a grid spacing of 3 km or smaller) is necessary to capture small‐scale river and stream networks and associated shallow water tables, and supply crop and plant root‐zone water double that of low‐resolution simulations, which is critical to replenishing the depleted vegetation root zones and leads to 150 mm more evapotranspiration. Including groundwater processes in high‐resolution models is effective to reduce: (1) 2‐m temperature warm biases from 5–6 to 2–3 °C and (2) the low precipitation bias by half. The additional groundwater supply to active soil flux in high‐resolution simulations with groundwater for June‐August is nearly translated into the same amount of increased precipitation in the domain investigated. Key Points Groundwater‐atmosphere nexus heavily depends on model resolution and is accelerated at convection‐permitting scales Convection‐permitting simulations with groundwater effectively mitigates summer warm and dry biases in central United States The amount of water transported from shallow water tables to plant root zon