A map of the wind speed over the Baltic plotted using the WRF model (11.06.2015, 12:00)

The wind speed and direction at a height of 10 m above the surface, obtained using a numerical weather model (representative of a 4×4 km area).

Wind speed is one of the basic variables in numerical weather models. The SatBałtyk system uses the WRF model (Weather Research and Forecasting), one of the most commonly used mesoscale weather models worldwide (suitable for analysing weather phenomena at a scale of several tens to several hundreds of kilometres, that is, a scale corresponding to the size of the Baltic Sea).

In the SatBałtyk System, the WRF model covers the whole area of the Baltic Sea and uses the results of a global weather model as a source of information about adjacent areas. The details regarding the WRF model and its configuration in the SatBałtyk System can be found here.

The SatBałtyk System service provides distributions of wind speed over the Baltic in the form of vectors with colours corresponding to wind speeds measured in m/s, 24 times a day, in the form of vector maps (direction of the arrow = direction of the wind, colour and size of the arrow = wind speed).

Methodology for determining wind speed and direction 

Wind speed is the horizontal component of the three-dimensional velocity of air movement.  In the WRF model, like all the other variables describing the state of the atmosphere, it is determined on a three-dimensional grid covering the section of the atmosphere over the target area from the land/sea surface to the 50 hPa level, which lies at an altitude of approximately 20 km. The components of wind speed at the various grid nodes are obtained as the solution of the equation that describes the movements of air with respect to the forces acting on them (inter alia pressure gradient forces, the Coriolis force, surface friction forces).

In the WRF model, the layers of the atmosphere are of different thicknesses, variable in time and space, and dependent on the land relief and the state of the atmosphere at a given place. In order to obtain the wind speed at a height of 10 m above the surface, which is a product of the SO SatBałtyk system, the model results are interpolated in the vertical.

Validation (assessment of accuracy)

The accuracy of the wind speed maps is assessed on the basis of an analysis of the differences between measured and modelled wind speed values. The results of the model’s validation can be found here.

Link to the parameter in SatBaltic System:

Wind speed and direction (for registered users)