The preliminary evaluation of wind field forecast of Aladin/Croatianumerical model

摘要

The subjective evaluation of the wind field forecasted by Aladin/Croatia mesoscale numerical model with 8-km horizontal resolution in both direction for every three hour 48 hours in advance was done. The Limited Area Model Aladin is in fact a version of a global model Arpege using about 70% of common code, the main differences being the geometry, the bi-periodicitisation and the coupling with the large scale solution and the bi-Fourier transforms. Since January 2001, Aladin is pre-operationally run on a Croatian domain. This domain covers the Alps, Dinaric Alps and part of the Adriatic Sea. Output surface wind fields on the Croatia domain are dynamically adapted to orography with 2-km resolution. The subjective evaluation was used to show the utility of the model for operational weather forecasting. The limited case studies were used to highlight the model capabilities and limitations in forecasting the direction, velocity and the onset of the sea breezes and the strong katabatic wind bora in two different summer synoptic situations over the Adriatic coast. One was on 2nd and another on 11th of August 2001. The first results from subjective verification suggest the wind forecast from Aladin/Croatia model is more useful fro strong wind like bora and for the some localities were sea breezes were canalized and developed moderate strong. The method of dynamical adaptation is based of fundamental assumption that the wind at the surface depends on synoptic forcing. Since the bora is katabatic wind, which strongly depends upon orography the method of dynamical adaptation to 2-km resolution representation of orography, definitely brought some progress. The model quite well forecasted the direction and the onset of the stronger wind in space and time. The objective statistics do not indicate in which situation model give more accurate forecast guidance what is important particularly for providing special local forecast. That is the main reason for further developing subjective evaluation on more weather situations and events.