Differences in wind speeds according to measured and homogenized series in the Czech Republic, 1961–2015
|Článek v odborném periodiku
|Časopis / Zdroj
|International Journal of Climatology
|Fakulta / Pracoviště MU
|Czech Republic; homogenisation; measurements; stilling; trends; wind speed
|Non-meteorological factors may bias wind speed measurements in a number of ways, among them the types of instruments used, their calibration and standards of maintenance, station relocations, and changes in the physical surroundings of a given station. Moreover, homogenisation of series of such measurements is more complicated than that of other climatic variables. This contribution uses figures from the Czech Republic as an example to demonstrate that measured (raw) data may produce different results in mean daily wind speeds from those acquired in homogenous series. A basic set of measurements taken in 1961–2015 at 178 meteorological stations was quality-checked and then homogenized using the Standard Normal Homogeneity test (SNHT) and the Maronna-Yohai test. Subsequent analyses were based on homogenized series from 119 stations. Station relocations and automation of wind speed measurements were identified as the most important sources of break-points in series of mean daily wind speeds. Generally lower mean wind speeds (as well as wind speed variability) were obtained from homogenous series in comparison with measured data, with reflections also found in their spatial distribution around the territory of the Czech Republic. Statistically significant decreasing linear trends calculated from measured and homogenized daily wind speed series from 119 stations confirm the existence of wind stilling as a typical feature of land mid-latitudes in recent decades. However, trends from measured data are highly overestimated compared with those from homogenized series.