A wind measurement mast (called just "mast" in the following) disturbs the free wind flow in several ways: The strongest effect is a pronounced decrease of the wind speed downwind of the mast due to mast shadowing. A decrease also occurs upwind of the mast due to flow retardation, but to an extent smaller by far than downwind of the mast. At the lateral mast edges perpendicular to the flow direction, a small increase of the wind speed occurs due to dynamic flow speed-up.
These mast effects onto the wind speeds can be corrected by evaluating the wind speeds of two anemometers appropriately. WIND DATA SUiTE has developed a method which is based on so-called characteristic distortion waves (CDW). This method is described in detail in the WIND DATA SUiTE Report No. 2018-11.
The method is generally applicable and independent of mast configuration, mast location, anemometer location on the mast, and air stratification conditions.
In the following example, an anemometer No.3 is mounted at a height of 120m a.g.l. on a boom directed towards south. An anemometer No.2 is mounted at a height of 120m a.g.l. (set to 121m for WDS wind profile compliance) on a boom directed towards north.
Fig.1 shows an excerpt of the wind speed time series of anemometer No.3 before (v3) and after (v3c) the mast correction at the time, where the greatest wind speed correction occurs. Fig.2 shows an excerpt of the wind speed time series of anemometer No.2 before (v2) and after (v2c) the mast correction at the time, where the greatest wind speed correction occurs.