Effects of sub-grid variability of precipitation and canopy water storage on climate model simulations of water cycle in Europe

The impact of sub-grid variability of precipitation and canopy water storage is investigated over Central-South Europe by applying a new canopy interception scheme into the Community Atmosphere Model (CAM, Version 3) coupled with the Community Land Model (CLM, Version 3). The study shows that while sub-grid variability exerts great impact on the land surface water budget, the impact on the atmospheric hydrological processes is small and only exception being the Mediterranean region. In this region, incorporation of sub-grid variability is shown to reduce precipitation up to 1 mm/day (or ~8% relative to mean precipitation). The evapotranspiration ratio (ratio of evapotranspiration to total precipitation) exhibited insignificant deviations between the simulations with sub-grid variability and the ones without, which indicates that the local source of moisture is not the cause of the reduced precipitation. On the other hand, inducing sub-grid variability alters the large-scale circulation, which transports less water vapor form Atlantic Ocean to inland areas thus reducing precipitation in the Mediterranean region.