This parameter is the natural logarithm of the length of the heat roughness. The surface roughness of heat is a measure of the resistance of surface heat transfer. This parameter is used to determine the air to surface transfer of heat. For a given atmospheric condition, higher surface roughness means that it is more difficult for air to exchange heat with the surface. A lower surface heat roughness means that air is more likely to exchange heat with the surface. On the ocean, the heat roughness of the surface depends on the waves. On sea ice, it has a constant value of 0.001 m. On land, it comes from vegetation types and snow cover.
