The hydrologic cycle over land includes interception of water by plant foliage and wood, throughfall and stemflow, infiltration, runoff, soil water, and snow (see figure).

These are directly linked to the biogeophysics and also affect temperature, precipitation, and runoff (see figure).

Total runoff (surface and sub-surface drainage) are routed downstream to oceans using a river routing model.

Major global river systems are clearly evident in the model ouput (see figure).

NB: This is unpublished material intended to illustrate our work.

Global 20-Year Simulation

A river transport model (RTM) (Branstetter et al., in prep) is synchronously coupled to the Community Land Model (CLM) for hydrological applications as well as for improved land-ocean-sea ice-atmosphere coupling in the Community Climate System Model (CCSM).

We have implemented this model on a 1/2 degree grid. Code internal to the land model interpolates the total runoff from the column hydrology (e.g., T42, T31 grid) to the river routing 1/2 degree grid (see figure).

Shown here for illustration are results from a global 1° by 1° simulation using the NCAR LSM operated in the same synchronous land-river framework. The model is driven with NCEP data from 1979 to 1998. Vegetation cover and density are prescribed using monthly data derived from satellite products (Bonan et al., 2002).

Branstetter, M.L., J.S. Famiglietti, and A.P. Craig, Parallelization and performance of a river transport model for use in global climate models, in prep.

Bonan, G.B., S. Levis, L. Kergoat, and K.W. Oleson, Landscapes as patches of plant functional types: An integrating concept for climate and ecosystem models. Global Biogeochem. Cycles, 16, 2002.