Potential Negative Effects of Groundwater Dynamics on Dry Season Convection in the Amazon River Basin

Monday, 15 December 2014
Yen-Heng Lin, National Taiwan University, Taipei, Taiwan, Min-Hui Lo, NTU National Taiwan University, Taipei, Taiwan and Chia Chou, Research Center for Environmental Changes Academia Sinica, Taipei, Taiwan
Adding a groundwater component to land surface models affects modeled precipitation because the additional water supply from the subsurface contributes to increased water vapor in the atmosphere, resulting in modifications of atmospheric convection. This study focused on how groundwater dynamics affect atmospheric convection in the Amazon River Basin (ARB) during July, typically the driest month. Coupled groundwater-land-atmosphere model simulations show that groundwater storage increases evapotranspiration rates (latent heat fluxes) and lowers surface temperatures, which increases the surface pressure gradient and thus, anomalous surface divergence. Therefore, the convection over the Southern Hemispheric ARB during the dry season becomes weaker when groundwater dynamics are included in the model. In addition, the changes in atmospheric vertical water vapor advection are associated with decreases in precipitation resulting from downward transport anomalies. The results of this study highlight the importance of subsurface hydrological processes in the Amazon climate system, which have implications for precipitation changes during the dry season observed in most current climate models.