1. Evaluation of AROME Model Valley Wind Simulations in the Inn Valley, Austria : Sensitivity to Horizontal Grid Resolution
- Author
-
Wibmer, Benedikt and Wibmer, Benedikt
- Abstract
The aim of this Master’s thesis was to evaluate valley wind simulations with the numerical weather prediction model AROME (Application of Research to Operations at MEsoscale) within the Inn Valley, Austria. By means of a case study, the research concentrated on IOP8 of the CROSSINN field campaign, characterized by the establishment of thermally driven winds. A special focus was put on the impact of moving to sub-km horizontal grid resolution, by applying the AROME-Aut configuration of GeoSphere Austria at three distinct grid spacings: 0.5 km, 1.0 km and the currently operational 2.5 km. It was found that the representation of thermodynamic conditions, both over the Alpine foreland and in the valley atmosphere is crucial for reproducing the observed along-valley wind magnitudes in the Inn Valley. As all simulations exhibit a systematic warm bias (up to +2 K) for the nocturnal valley boundary layer, the thermal forcing and, hence, downvalley winds were generally too weak in the morning. During the second night, all simulations exhibit persistent upvalley winds which ceased at around midnight in the observations. This discrepancy is related to the combined effect of cold air advection in the Alpine foreland and the nocturnal warm bias in the valley atmosphere, thus missing the reversal of the hydrostatic horizontal pressure gradient to the foreland in the simulations. Furthermore, the 0.5- km simulation was severely impacted by the lateral boundary conditions during the second night, by advecting colder air into the smaller model domain, thus enhancing the thermal forcing for the persistent upvalley winds. While the interaction with synoptic-scale winds (forced channeling) in the Inn Valley entrance region showed a potential contribution to the persistent upvalley winds in the simulations, this was not supported by ERA5-reanalysis data and could not be quantified with the available observations. Although, the reduction of horizontal grid spacing showed only marginal in, Masterarbeit Universität Innsbruck 2024
- Published
- 2024