Meteorological Research Institute CGCM Version 3

From this paper describing the model:

e. Land surface model

A new land surface model named the Hydrology, Atmosphere and Land (HAL) model (Hosaka et al. in preparation) has been developed for MRIAGCM3. HAL consists of three submodels: SiByl (vegetation), SNOWA (snow), and SOILA (soil).

h. River-lake model and ice discharge from ice-sheet

The river-flow component in MRI-AGCM3 is the Global River model using TRIP (GRiveT ). The river-channel dataset we use for MRICGCM3 is the 1 1 version of the Total River Integrated Pathway (TRIP) (Oki and Sud 1998). River runoff is calculated by the land surface model in MRI-AGCM3 and is transported by GRiveT to the river mouths via TRIP. GRiveT also has a lake in each TRIP grid, which is connected to the lake surface component in MRI-AGCM3. The river and lake water masses and their internal energies are predicted. The water runoff estimated by the land surface component and precipitation minus evaporation by the lake-surface component are input to GRiveT. In each grid, river water flows at a constant velocity of 0.4 m s1. Half of the river water flows into the lake, and the lake water returns to the river, depending on the water level, with a 10-day e-folding timescale. The internal energies are affected only in the lake by the surface heat fluxes estimated at the lake-surface component, and are reflected on the ocean temperature when they are discharged at the river mouth. Freezing of the lake is not considered. As MRI-CGCM3 does not include a dynamic ice-sheet model, a simple model for snow on ice sheet (SMIST ) is used as the ice-sheet component of MRI-CGCM3 in order to balance the global ocean water mass in the unforced climate. When the SWE is greater than 10 m over the land surface, the excess snow is taken away from the land surface model and passed to SMIST. The ice mass and its energy are transported to the ocean coast by SMIST and discharged into the ocean as an iceberg. The algorithm is almost the same as the GRiveT algorithm, but without any lake.

This model's treatment of lakes is focused on the routing of water and does not simulate ice cover 

This is a technical summary of the atmosphere component, which includes a section (3.8) on GRiveT.  It is similar to the section above.