A Catchment-Based Global River Routing Scheme for Climate Models and Assimilation of Streamflow and Altimetry Data
James S. Famiglietti, Francisco Olivera, Jeffrey P. Walker, Paul R. Houser, Matthew Rodell and Marcia L. Branstetter
While the vertical exchanges of water, energy, and momentum are reasonably well simulated in the land component of climate models, lateral surface water transport, from its point of origin in continental interiors to continental margins (i.e.river transport), is poorly if at all represented. This deficiency must be addressed for numerous reasons, including global water cycle closure in fully-coupled climate system models (CSMs); to ensure mass and salinity balance in CSM component models; because the thermohaline circulation is very sensitive to continental freshwater outflows; and because the inclusion of rivers will allow for studies of climate change impacts on the distribution of flooding and fresh water availability, and for validation of climate model simulated hydrographs against observations. Most current river transport schemes are cell-based and therefore limited in their capabilities to properly represent land-surface hydrology and to exploit the availability of high resolution digital elevation data, recent advances in hydrologic data assimilation and upcoming opportunities in surface water remote sensing. The purpose of this presentation is to discuss a new, catchment-based, global river transport scheme for use in GCMs and coupled CSMs that overcomes the shortcomings of cell-based models. Distinguishing features of the model are that it will be catchment- rather than grid cell-based, and that it will have an explicit representation of river networks and lakes/reservoirs that will enable assimilation of in situ stream gauge data and altimetric observations of stream and lake/reservoir elevations. Model development and plans for assimilation will be discussed.