Lakes and wetlands can comprise a large fraction of the land surface. In regions of high inland water, they have a significant impact on climate because of differences in albedo, heat capacity, roughness length, and energy exchange compared to vegetated surfaces. I used version 0 of the NCAR Land Surface Model, coupled to a modified version of the NCAR Community Climate Model version 2, to examine the effects of inland water bodies on climate. The land surface model allows for multiple surface types within a grid cell. A lake/swamp model is used to calculate surface fluxes and temperatures for the fractions of the grid cell covered by lakes and wetlands.
In July, the presence of water bodies results in a spatially consistent signal in which high inland water regions are 2 to 3C cooler, have increased latent heat flux (10 to 45 W/m2), and decreased sensible heat flux (5 to 30 W/m2) compared to a simulation without inland water. These changes are statistically significant (based on 5-year simulations) in the lake region of NW Canada, the Great Lakes region of North America, the swamp and marsh region of the Siberian lowlands, and the lake region of East Africa. January effects were difficult to interpret due to large interannual model variability. In East Africa, the January (wet season) signal was less than the July (dry season) signal.