Wind resource assessments with onsite wind data are indispensable when estimating the economic feasibility of developing a large-scale commercial offshore wind farm. However, several factors of the data measured from a meteorological mast, including short observation period and instrument errors, may result in uncertainty concerning wind resource assessments. To mitigate the uncertainty of wind resource assessments at the candidate site for a large-scale commercial offshore wind farm, HeMOSU-1, the first offshore meteorological mast in Asia, has been in operation for more than 6 years since it was installed at the western coast of the Korean Peninsula in 2010. A vertical wind lidar was also installed for quantitative evaluations and calibrations of the measured data from HeMOSU-1. This study analyzed several parameters associated with the long-term wind characteristics through cross-validation between HeMOSU-1 and the wind lidar. The parameters affecting the prediction results include the shading effect from the mast, year-to-year variation, the long-term correction methods, and the period of onsite measurements. Based on this analysis, long-term wind potentials are estimated with reliable parameters. (C) 2018 Elsevier Ltd. All rights reserved.