Validation of near-surface wind speed monthly averages from CHELSA climate data in Croatia

This study validated monthly averages of near-surface wind speed (NSW) from the 1km Climatologies at high resolution for the earth’s land surface areas (CHELSA) climate data using long-term ground truth data from 22 climate stations operated by the Croatian Meteorological and Hydrological Service (DHMZ). The CHELSA NSW monthly averages resulted in the coefficient of determination (R²) from 0.390 to 0.691 and the normalized root mean square error in range of 0.409–0.635. A significant difference in validation results was observed between the October-April and March-September periods, with mean R² values of 0.655 and 0.442, respectively. There is a slight temporal discrepancy between CHELSA v2.1 (1981–2010) and the latest official DHMZ climate data (1971–2000), which may affect the accuracy of CHELSA data in Croatia. However, it could also indicate the effects of climate change on NSW, which produced higher residuals from DHMZ ground truth data in warmer May–September period and in coastal DHMZ climate stations. To complement on the current study, future research should resolve the temporal delay with the eventual publication of more recent ground truth data from DHMZ. Additionally, similar open climate datasets should be included to determine the most suitable 1 km resolution climate data source in Croatia.