Description of the upgrade

The following modifications were implemented:
Modifications to the cloud and radiation subroutines, both to improve the cloud/radiation processes and to facilitate their use with increased vertical resolution. In particular, the overlapping of cloud layers was changed from a random overlap to a maximum overlap assumption.
A revised scheme for vertical diffusion in the free atmosphere, developed following the switching off of vertical diffusion above the PBL in 1988; the vertical mixing represented by the revised scheme is smaller by an order of magnitude than under the scheme which was operational until 1987.
Two revisions to the convection scheme, to ensure consistent cloud physics within the cloud model, and to introduce a cloudtop temperature check to improve the onset determination of shower precipitation.

Implemented: 09 April 1991