engleski

Validation od mesoscale near-surface winds obtained with ALADIN mesoscale NWP model in complex terrain of Croatia

Mesoscale numerical models of progressively finer horizontal resolution are used to refine wind predictions in the complex terrain, where wind climate is governed by regional and local winds. As traditionally used moment-based verification measures (like RMSE, MBIAS, MAE, etc.) are not always able to show the benefits of higher resolution models, we utilized spectral analysis as a supplementary verification method to provide a scale-dependent measure of model performance. An emphasis is on understanding the sources of prediction errors through relating various aspects of physical and spectral verification measures. The verification was performed on wind forecasts obtained by ALADIN mesoscale NWP model with 8 km horizontal grid spacing in period 2010-2012. These forecasts were further refined to 2 km grid spacing using: i) full-physics based model and ii) so-called dynamical adaptation method (DADA). Based on variety of statistical and spectral scores, it is suggested that wind speed forecast generally improves with increasing the model horizontal resolution. The largest portion of root-mean square errors (RMSE) can be attributed to phase errors at majority of stations, while the most significant increase of accuracy was found for diurnal and sub-diurnal periods of motions. Furthermore, we found a significant correlation between different sources of RMSE errors and spectral scores related to synoptic, diurnal and sub-diurnal motions. Finally, it was shown that non-hydrostatic and full-physics based model at 2 km horizontal resolution was valuable in forecasting wind properties at stations with significant portion of weaker, thermally driven flows.

wind speed forecast; ALADIN; moment-based verification measures; spectral analysis

IPA projekt WILL4WIND, IPA2007/HR/16IPO/001-040507