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

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 degrees 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.

Automated summary

This study shows that a smaller grid spacing is needed to capture the impacts of groundwater processes on the water balance and hydrometeorology, and including groundwater processes in simulations can reduce temperature and precipitation biases and increase evapotranspiration.