Description of the upgrade

A revised vertical diffusion scheme was implemented. The turbulent diffusion is now limited to below the top of the boundary layer except when static instability is generated. This modification restricts the vertical mixing to the boundary layer. The reduction of dissipation and momentum and heat mixing in the free atmosphere has a positive impact on zonal mean temperatures and reduces the zonal wind errors. The eddy activity becomes stronger.
Modest modifications in the parametrisation of the surface processes were included. The revision of the numerical scheme affects the partitioning of the surface moisture flux in terms of water extraction from the various contributing reservoirs. The interaction between convective precipitation and surface hydrology was revised as well as the interaction between the radiation and both the canopy layer and the snow.
The new surface parameters are only marginal influenced by these changes except in the case when snow is melting. Now the surface temperatures are allowed to be positive even with snow on the ground.

Implemented: 05 January 1988