9.0 POST-IMPLEMENTATION CHANGES

Because of problems found in the weeks following this implementation the following changes were made to the system:

On 24 June at 1200Z a correction was made to the analysis system to speed the rate of convergence of the iterations. This is expected to reduce the level of noise in both the analysis and the forecast]
Additional changes were made to the system on 1200Z Tues 21 July as follows:

1. A convective adjustment was added to the grid-scale precipitation code to remove remaining local static instability not eliminated by the convection scheme. This change has been shown in full-resolution tests to systematically damp tropical vortices. Spurious tropical vortices will still appear, but they will be considerably weaker.

2. A substantial increase was made in the horizontal diffusion for the small-scale end of the spectrum

3. A set of changes was made to reduce (but not eliminate) the warm bias over land:

elimination of short-wave absorption by aerosols
correction of error in surface albedo
increase in evaporation from vegetation (thus reducing sensible heating and increasing latent heating over areas with vegetation)

Changes (1) and (2) were tested in a parallel system at T170 resolution, while the changes in (3) (which are not resolution-dependent) were tested at T62. Then, the entire package was tested in the T170 parallel system from July 17 through July 21.

The map files are labeled in the form [mdd]f[hh].gif, where m=month, d=day, and hh= forecast hour, e.g., 717f12.gif is the 12-h forecast from 17 July. All forecasts originate at 00Z.