Abstract : C.2
Downscaling of future precipitation scenarios for western Norway - a simple physical method approach

Idar Barstad
idar@gfi.uib.no
Bjerknes Centre for Climate Research - University of Bergen

A linear orographic precipitation model (Smith and Barstad, 2004; JAS) with a crude representation of airflow dynamics and microphysics has been used to downscale the large-scale climate runs over the western part of southern Norway. The IPCC control runs for the last 40 years, reanalysis (ERA40) and future scenarios are downscaled. The output results show statistics for both annual precipitation and the daily extremes valid for a 1 km grid. Preliminary results show that a 12% mean increase in daily precipitation is expected for the region in question.

Although the linear model has its limitations, the modelís performance has proven well in earlier studies, both reproducing annual and daily precipitation patterns in a comforting manner. The method is computationally efficient and put no demands on supercomputers. Furthermore, realization of future climate scenarios consist of many global circulation model runs, and conventional downscaling tools may become too costly. In this way, simple, physically-based methods has the potential to become very useful estimating local precipitation in mountainous areas.

(An extended abstract will appear at: http://www.uib.no/People/ngfib/privweb/engelsk.html)