Title: 2.12. Lake Model — ctsm CTSM master documentation

URL Source: https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Lake/CLM50_Tech_Note_Lake.html

Markdown Content:
The lake model, denoted the _Lake, Ice, Snow, and Sediment Simulator_ (LISSS), is from [Subin et al. (2012a)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#subinetal2012a). It includes extensive modifications to the lake code of [Zeng et al. (2002)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#zengetal2002) used in CLM versions 2 through 4, which utilized concepts from the lake models of [Bonan (1996)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#bonan1996), [Henderson-Sellers (1985)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#henderson-sellers1985), [Henderson-Sellers (1986)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#henderson-sellers1986), [Hostetler and Bartlein (1990)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#hostetlerbartlein1990), and the coupled lake-atmosphere model of [Hostetler et al. (1993)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#hostetleretal1993), [Hostetler et al. (1993)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#hostetleretal1993). Lakes have spatially variable depth prescribed in the surface data (section [External Data](#external-data-lake)); the surface data optionally includes lake optical extinction coeffient and horizontal fetch, currently only used for site simulations. Lake physics includes freezing and thawing in the lake body, resolved snow layers, and “soil” and bedrock layers below the lake body. Temperatures and ice fractions are simulated for \\(N\_{levlak} =10\\) layers (for global simulations) or \\(N\_{levlak} =25\\) (for site simulations) with discretization described in section [2.12.1](#vertical-discretization-lake). Lake albedo is described in section [2.12.3](#surface-albedo-lake). Lake surface fluxes (section [2.12.4](#surface-fluxes-and-surface-temperature-lake)) generally follow the formulations for non-vegetated surfaces, including the calculations of aerodynamic resistances (section [2.5.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#sensible-and-latent-heat-fluxes-for-non-vegetated-surfaces)); however, the lake surface temperature \\(T\_{g}\\) (representing an infinitesimal interface layer between the top resolved lake layer and the atmosphere) is solved for simultaneously with the surface fluxes. After surface fluxes are evaluated, temperatures are solved simultaneously in the resolved snow layers (if present), the lake body, and the soil and bedrock, using the ground heat flux _G_ as a top boundary condition. Snow, soil, and bedrock models generally follow the formulations for non-vegetated surfaces (Chapter [2.6](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.html#rst-soil-and-snow-temperatures)), with modifications described below.

