Modal view of atmospheric circulation

representation of  the atmosphere

MODES performs decomposition of global circulation in terms of three-dimensionally orthogonal eigensolutions (Hough harmonics) of the linearized primitive equations. In this way, spatial and temporal variability associated with the two main circulation regimes, the Rossby and inertia-gravity regime, can be quantified across scales. 3D linear wave theory is most useful in the tropics where two special wave solutions, the Kelvin wave and the mixed Rossby-gravity wave, accounting for a significant part of tropical variability, obliterate the distinction between fast and slow dynamics in the midlatitudes.

A book on the applications of normal-mode functions in weather and climate dynamics and numerical weather prediction research:


Modal decomposition of ECMWF deterministic forecasts


Atmospheric energy spectra

Distribution of atmospheric balanced and inertio-gravity energy as a function of the zonal wavenumber.

Circulation maps

Horizontal circulation maps of the Northern and Southeren Hemisphere and the Tropics.

Equatorial cross-sections

Longitude-altitude diagram of the tropical zonal winds associated with the balanced and inertio-gravity circulation and the equatorial Kelvin wave.

Hovmöller diagrams

Ten-day evolution of the tropical winds on selected levels.

Kelvin waves

Evolution of the Kelvin wave in the ECMWF model forecast and comparison with analyses.

Polar maps

Polar maps of horizontal winds in the Northern Hemisphere (40°N-90°N)