CR prepress abstract - doi: 10.3354/cr01464
Spatial and temporal variability of mean daily wind speeds in the Czech Republic, 1961–2015
Rudolf Brázdil, Pavel Zahradníček, Ladislava Řezníčková, Radim Tolasz, Petr Štěpánek, Petr Dobrovolný
ABSTRACT: This contribution analyses the spatio-temporal variability of mean daily wind speeds (MDWSs) over the territory of the Czech Republic in the 1961–2015 period, using series from the 119 meteorological stations of the Czech Hydrometeorological Institute. These series were quality-controlled and homogenised by application of the Standard Normal Homogeneity Test, after Alexandersson, and the Maronna and Yohai test. The spatial variability of MDWSs is analysed in terms of annual and seasonal data, which exhibit a clear relationship to orographic character, with the highest values in the highland and mountain areas. The spatial relationships between stations are interpreted by means of correlation graphs, which express the dependence of MDWSs on the altitude of the stations and the distance between them. Analysis of monthly, seasonal and annual linear trends for four altitudinal intervals and the entire Czech Republic shows a decreasing tendency, almost statistically significant (significance level α = 0.05). Taking the 119 stations individually, a certain proportion of stations also display positive trends. Comparison of MDWS variability with circulation indices shows a closer relationship to the Central European Zonal Index than to the North Atlantic Oscillation Index. The results obtained are discussed with respect to the problems associated with wind speed measurements, particularly the change from standard to automatic wind speed measurements, and a broadly-occurring decline in measured wind speed series in recent decades (“wind stilling”).