Generating artificial vertical soundings over complex terrain from the aLMo model output to drive a high resolution snow-drift model

Abstract

To obtain a high-resolution wind field and to model snow drift over complex topography, the Swiss Federal Institute for Snow and Avalanche Research (SLF) uses the atmospheric model ARPS (Advanced Regional Prediction System, University of Oklahoma). ARPS accesses horizontally homogeneous initial fields. Until recently, this model was driven by atmospheric soundings recorded at sites far away from the actual model domain. In order to optimise the initial conditions of ARPS and to provide the option of producing real forecasts, a new downscaling method has been developed, which can also be applied to other uses. Based on the vertical structure of the atmosphere produced by the operational mesoscale forecast model aLMo (Alpine Model, MeteoSwiss), an artificial sounding is created for a specified location within the ARPS grid. Some of the techniques applied include model bias adjustment (based on aLMo verification studies), the introduction of horizontal filters, the assimilation of surface observation data and the vertical displacement of the boundary layer, motivated by the distinct topographies of the ARPS and the aLMo model. The combination of the methods differs from parameter to parameter. This paper describes details of the downscaling technique and gives an example of the application of the method.

Fine‐scale modeling of the boundary layer wind field over steep topography

“…2003; Spreitzhofer and Raderschall, 2004]. Initializing the ARPS model with such a sounding, it can be used in a simplified forecast mode.…”

MetGIS™: combination of Meteorological and Geographic Information Systems to produce high resolution mountain weather forecasts

“…MetGIS ™ was constructed having the latest techniques of software engineering (Dumke, ; Endres and Rombach, ) and basics of geographic information systems (Jones, ; Burrough and McDonnell, ) in mind. The code consists mostly of Java‐based object‐oriented approaches (Lorenz, ; Naughton and Schildt, ) and some graphics libraries that have already been employed in the construction of the successful snow cover visualization software SN_GUI (Spreitzhofer et al , ).…”

“…The downscaling module uses the high‐resolution geographic information included in MetGIS ™ to assess meteorological information for scales much smaller than those resolved by operational mesoscale models. It relies on a combination of algorithms developed by Spreitzhofer and Raderschall () and ‘VERA‐style’ techniques. VERA (Vienna Enhanced Resolution Analysis, Steinacker et al , , ) incorporates an objective, automated downscaling and analysis approach for meteorological data over complex topography.…”