Comparison of HIRLAM wind data with measurements at Estonian coastal meteorological stations

Abstract

The possibilities of using High Resolution Limited Area Model (HIRLAM) version 6.4.0 outputs to describe wind parameters in the coastal zone of Estonia were investigated. For this purpose output from 3-dimensional variational (3DVAR) analysis and 24 h forecast files were compared with measurements at nine coastal sites during January and April–December 2007. Special attention was paid to moderate and strong winds (wind speed > 5 m/s) that are responsible for sea level changes and high wave heights in the coastal area. It is shown that HIRLAM overestimates the wind speed. This overestimation is stronger in cases where HIRLAM uses an inadequate land–sea fraction in the respective cells. The model describes the angular distribution of moderate and strong winds better than that of weak winds. Except for one station, approximately 90% of HIRLAM estimates of the direction of moderate and strong winds differ less than ± 22.5° from the measured values; in approximately 60% of cases the direction differs less than ± 10°. The HIRLAM system approximates best the winds at the westernmost stations on the Estonian islands and in Pärnu, whereas a 24 h forecast gives somewhat better results than the winds diagnosed from 3DVAR analysis.

Keywords

• HIRLAM version 6.4.0
• wind speed
• wind direction
• Estonian coastal sea