HR: 09:48h
AN: A51F-09    [Abstracts]
TI: The Impact of Water Table Dynamics on Regional Climate
AU: * Weaver, C P
EM: weaver@cep.rutgers.edu
AF: Center for Environmental Prediction, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States
AU: Miguez-Macho, G
EM: gonzalo@envsci.rutgerrs.edu
AF: Center for Environmental Prediction, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States
AU: Reinfelder, Y F
EM: yingfan@rci.rutgers.edu
AF: Center for Environmental Prediction, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States
AB: The water cycles in the land and atmosphere make up a fundamentally coupled system, with complex interactions among all reservoirs (atmosphere, soil-vegetation, groundwater, and rivers) over a wide range of space and time scales. Our focus is on the role of the groundwater reservoir in this land-atmosphere coupling: the water table's dynamical interaction with infiltration, stream flow, and evapotranspiration, its control of the spatio-temporal organization of soil moisture, and hence its impact on atmospheric processes such as precipitation. Our hypothesis is that the water table dynamics plays an important role in land-atmosphere interactions and feedbacks, and thus the regional climate system. To date, however, no study has investigated the three-dimensional, dynamic coupling between all of the reservoirs, atmospheric, surface, and subsurface, of the terrestrial water cycle. Our goal is to address this fundamental gap in our knowledge. The key to understanding the role of the water table in the two-way coupling between land and atmosphere lies in its influence on the soil water content near the surface and in the root zone. In particular, the water table depth controls the equilibrium soil water profile in the unsaturated zone. Therefore, the characteristic spatial and temporal organization of water table depth (that reflects its governing dynamics) is communicated to the soil moisture field, and in turn, via surface-atmosphere fluxes, to the atmosphere. At the same time, the surface and subsurface hydrology responds strongly to atmospheric processes such as evaporative demand and the distribution, frequency, and intensity of precipitation. We wish to understand the implications of this two-way linkage for our current understanding of land-atmosphere feedbacks, e.g., between soil moisture and convective rainfall. Answering these questions requires a tool capable of studying the integrated terrestrial water cycle. Until now, no such tool was available. To address this need, we have built the fundamental groundwater and river flow processes into the Regional Atmospheric Modeling System (RAMS), including a prognostic, process-based boundary condition (i.e., the water table) for the unsaturated soil column, a mass balance for the saturated storage which governs the water table dynamics, lateral groundwater flow from cell to cell, two-way groundwater-stream interaction within a cell, surface runoff to local rivers, and continental river routing to the ocean. With our new tool, it is now possible to study the co-evolution of the water table, soil moisture, atmospheric circulation, clouds, and precipitation, along with the feedbacks that link them, in the context of one internally consistent model system. Here we report on results from preliminary numerical experiments with our new modeling system over the continental U.S. during the warm season. These experiments show that the inclusion of full water table dynamics in a regional climate simulation has a strong impact on the spatial and temporal organization of soil moisture at continental and large river basin scales, and that this impact is felt by the surface fluxes of sensible and latent heat, thereby driving changes in atmospheric dynamics and precipitation. Implications for land-atmosphere feedbacks will be discussed. In addition, the potential of this new tool for confronting a wide range of future integrated water cycle problems, e.g., in the areas of seasonal-to-interannual prediction, predicting and managing water resources, planning for weather-related emergencies, and projecting future coupled climatic-hydrologic changes due to natural and anthropogenic forcings, will also be discussed.
DE: 3322 Land/atmosphere interactions
DE: 3337 Numerical modeling and data assimilation
DE: 3309 Climatology (1620)
DE: 1836 Hydrologic budget (1655)
DE: 1655 Water cycles (1836)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting