The following calculations were made separately for each month at 9 stations/sites, which were located at Lapland (Käsivarsi and Sodankylä), coast of the Gulf of Bothnia (Hailuoto, Vaasa, and Rauma), coast of the Gulf of Finland (Hanko and Kotka), and inland Finland (Keski-Suomi and Kainuu).
First we search the minimum values for parameters RS and RD. The minimum values have to be selected among 194 = 130 321 possible combinations of years.
RS measures the representativeness with respect to the wind speed distribution: k is the shape parameter and A the scale parameter of the Weibull distribution, i refers to the parameter value in a combination of four years, and the overbar refers to the parameter value in the 19 year data set. The factor 6 is applied to make the deviations of A and k equally important for RS.
RD measures the representativeness with respect to the distribution of wind directions. D is the wind direction sector: D1 = 0-30°, D2 = 30-60°, and so on. V is the wind speed, and P is the percentage of cases in each wind direction sector.
The final parameter to be minimized is