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Global variable-resolution semi-Lagrangian vorticity-divergence NWP model

This study presents results from the application of a global variable resolution semi-Lagrangian vorticity-divergence numerical weather prediction (NWP) model developed by Mikhail Tolstykh at the Institute of Numerical Mathematics. Analyzed using ECMWF data from 1996, forecasts and data assimilation experiments conducted by M. Tsyroulnikov and colleagues showcase the model's performance. Key findings include geopotential errors versus radiosondes and the implementation of coordinate transformations to improve model efficiency. The extension to variable resolution techniques demonstrates minimal adjustments needed for current resolution codes while maintaining computational integrity.

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Global variable-resolution semi-Lagrangian vorticity-divergence NWP model

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  1. Global variable-resolution semi-Lagrangian vorticity-divergence NWP model Mikhail Tolstykh Institute of Numerical Mathematics Russian Academy of Sciences, and Russian Hydrometeorological Research Centre Moscow Russia

  2. Results of forecasts using ECMWF data for 1996

  3. Results of data assimilation experiments using RHMC OI (M.Tsyroulnikov, A.Bagrov, R.Zaripov) 08-28/02/2000 First guess geopotential errors vs radiosondes (red lines – 1.40625x1.125 deg model,blue lines -1.5x1.5 deg model, full line - RMS, dashed line - bias)

  4. NORD20 geopotential errors vs analyses

  5. Extension to the case of variable resolution in latitude • Discrete coordinate transfromation (given in the differential way, as a sequence of local map factors). This requires very moderate changes in the constant resolution code (introduction of map factors in computation of gradients, SI etc) and also allows to preserve all compact differencing and its properties intact. • Only one sphere is used everywhere. • Some changes in the semi-Lagrangian advection - interpolations and search of trajectories on a variable mesh.

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