Anemometry in icing conditions

The accuracy of wind measurements in icing conditions is discussed, and wind tunnel calibrations as well as field comparisons are presented for three heated anemometers that use different measuring principles. It is pointed out that ice-free anemometer calibrations, including those provided by manufacturers, are affected by the blockage effect in wind tunnels that are too small. Some anemometers that measure correctly in a wind tunnel give erroneous results in the field. Overall, measuring mean wind speeds and peak values in icing conditions with the accuracy of about 5% seems possible with the present technology, both with rotational and sonic anemometers, but in the most severe environments only some internally heated rotational anemometers are reliable. Wind measurements in icing conditions without due consideration of anemometer selection, specific instrument problems, calibration inaccuracies, mean vertical velocity component, and anti-icing of the supporting structures may result in very big errors.