Variable resolution global semi-Lagrangian atmospheric model

The variable resolution in latitude was implemented in the 3D global semi-Lagrangian finite difference numerical weather prediction model SL-AV. The implementation of the variable resolution is demonstrated by one of the model blocks, where the velocity field is reconstructed from vorticity and divergence. This block includes the solution of the Poisson equations on the sphere. Then this approach is validated in the context of a shallow-water model on the sphere by the set of standard tests. The results of the series of five-day forecasts by the 3D model show the benefit of using the variable resolution version of the model for three-day forecasts over Russia.