TY  - JOUR
A1  - Schmidli, Jürg
A1  - Böing, Steven
A1  - Fuhrer, Oliver
T1  - Accuracy of simulated diurnal valley winds in the Swiss Alps: influence of grid resolution, topography filtering, and land surface datasets
T2  - Atmosphere
N2  - We evaluate the near-surface representation of thermally driven winds in the Swiss Alps in a numerical weather prediction model at km-scale resolution. In addition, the influence of grid resolution (2.2 km and 1.1 km), topography filtering, and land surface datasets on the accuracy of the simulated valley winds is investigated. The simulations are evaluated against a comprehensive set of surface observations for an 18-day fair-weather summer period in July 2006. The episode is characterized by strong diurnal wind systems and the formation of shallow convection over the mountains, which transitions to precipitating convection in some areas. The near-surface winds (10 m above ground level) follow a typical diurnal pattern with strong daytime up-valley flow and weaker nighttime down-valley flow. At a 2.2 km resolution the valley winds are poorly simulated for most stations, while at a 1.1 km resolution the diurnal cycle of the valley winds is well represented in most large (e.g., Rhein valley at Chur and Rhone valley at Visp) and medium-sized valleys (e.g., Linth valley at Glarus). In the smaller valleys (e.g., Maggia valley at Cevio), the amplitude of the valley wind is still significantly underestimated, even at a 1.1 km resolution. Detailed sensitivity experiments show that the use of high-resolution land surface datasets, for both the soil characteristics as well as for the land cover, and reduced filtering of the topography are essential to achieve good performance at a 1.1 km resolution
KW  - valley winds
KW  - diurnal cycle
KW  - high-resolution simulation
KW  - land surface datasets
KW  - topography filtering
Y1  - 2018
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/51464
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-514644
VL  - 9
IS  - (5), 196
PB  - MDPI
CY  - Basel
ER  -