A preliminary sensitivity study of Planetary Boundary Layer parameterisation schemes in the weather research and forecasting model to surface winds in coastal Ghana

Abstract

There is growing interest in the use of Weather Researching and Forecasting (WRF) model for assessment of wind energy potential. The influence of parameterisation schemes in these models depends on meteorological processes, which tend to differ with geographic regions. In this paper, we test the sensitivity of surface winds in an area in Ghana, to 11 of the Planetary Boundary Layer schemes available in WRF. Thirty-six days were simulated with the schemes. Hourly simulated wind speeds and directions were compared with measurements taken at 40, 50, and 60m above ground level, and the schemes ranked according to a prediction skill score calculated according to how well their predictions compared to observations. The local closure MYNN schemes offered consistently good performance; often predicting the average wind speed with a Root Mean Square Error of less than <2 m/s, indicating good performance. However, the GBM and UW schemes produced relatively better results for days selected from a period in which monthly average winds at this location are highest. Based on our results, we recommend the MYNN3 (and the GBM, depending on the season of the year) for wind simulations in this area, and areas with similar topography and climate in Ghana.