A map of atmospheric pressure at sea level over the Baltic, plotted using the WRF model (11.06.2015, 12:00).

Atmospheric pressure at sea level obtained using a numerical weather map (representative of a 4×4 km area).

The atmospheric pressure 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 atmospheric pressure over the Baltic in hectopascals [hPa], 24 times a day, in the form of maps with a resolution of 4 km.

Methodology for determining atmospheric pressure   

In the WRF model, atmospheric pressure, like all the other variables describing the state of the atmosphere, 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 atmospheric pressures at the various grid nodes are obtained as the solution of the equations that express the conservation of a medium’s continuity and angular momentum, taking into account the forces acting on the air.

The  pressure values that the SatBałtyk System  provides relate to sea level, not to land surface level. This means that the atmospheric pressure over a land area is determined from the height of the point (pixel) in question above sea level, the pressure at that point and the hypothetical vertical temperature gradient typical of that area.

Validation (assessment of accuracy)

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

Link to the parameter in SatBaltic System:

Atmospheric pressure (for registred users)