Climatic study of the future drinking-water availability in Bergen, Norway, using a linear model for orographic precipitation
Abstract
Despite the rainy conditions on the west side of the mountains in southern Norway, there have been challenges in providing enough drinking water of high quality to the inhabitants of Bergen. Naturally, the municipality of Bergen is concerned about the provision of drinking water in the future, and will need some projections of the future supply for planning purposes. This work concentrates on the precipitation over the mountain "Gullfjellet". This mountain provides fresh water to the main reservoir in Bergen. It accounts for the water supply of 40 percent of the 260,000 inhabitants in the city. The starting point of the analysis is the output from 10 General Circulation Models from the European ENSEMBLES project - run with the SRES A1B scenario. The Smith-Barstad (2004) linear model of orographic precipitation is then used for downscaling. The input data for the linear model are velocity U, temperature T and static stability N (Brunt-Väisälä frequency). The model simulates precipitation by doing a Fourier transform, which include the orographic lifting-effect. The model includes user-defined time constants for conversion from cloud water to hydrometeor and fall-out of hydrometeors. This allows drift of cloud water and hydrometeors. In the event of zero-time constants, instantaneous precipitation of supersaturated water will occur. The linear model has been previously used to evaluate heavy precipitation in, among other places, mountain regions in the state of Washington, Germany, France and Norway. The linear model has been found to represent orographic precipitation over complex terrain well, describing the most essential dynamics and physics. The amount of leeside precipitation tends, however, to be overestimated. The analysis is done for the two time windows 2021 - 2050 and 2071 - 2100, and is being compared to the control period 1971 - 2000. Results from these model runs will be presented at the conference.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A53B0327K
- Keywords:
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- 3354 ATMOSPHERIC PROCESSES / Precipitation