Areal assessments of wind speeds and topography are necessary to determine the wind energy potential of an airshed, For such an assessment, the Point Cumulative Semi-Variogram (PCSV) concept is presented and applied to wind speed and topographic height records at a set of irregularly scattered sites over Turkey. The PCSVs have in their structure the combined effects of nearby site topography, wind speed and roughness features at the planetary boundary layer, On the basis of PCSVs, nearby site features are classified into five distinctive categories. The PCSVs provide useful information concerning the regional mutual relationships between the topographic and wind characteristics around each site. PCSVs for 35 wind speed measurement sites in Turkey are presented in detail with local interpretations and discussions. The application revealed that Turkish wind speeds are areally heterogeneous and have five categories. (C) 2001 Elsevier Science Ltd. All rights reserved.