The Impact of Grid Resolution on Fog and Low Stratus Modelling in Complex Terrain
Abstract
Fog and low stratus clouds affect various human activities such as airport procedures and photovoltaic energy production. Although current operational numerical weather prediction models run at kilometer-scale horizontal resolutions, forecasting of these clouds remains challenging. Previous studies have highlighted the need for high horizontal and vertical model resolutions to accurately simulate the interplay of the many small-scale processes which determine the fog and low stratus life cycle. We present a detailed analysis of the impact of horizontal and vertical grid spacing on a low stratus case in Switzerland simulated with the limited-area model COSMO-1. Specifically, we compare the model performance at 4 km, 2 km, 1 km and 500 m horizontal grid spacing with finely vs coarsely resolved topography. In the complex topography of Switzerland, high horizontal resolution is more critical than high vertical resolution. Higher horizontal resolution significantly improves the forecast in this case. Interestingly, the degree of detail of the topography is less important than the mere increase in grid points. Finely resolved topographic features even seem to promote too early stratus dissipation due to increased turbulent mixing. Our findings will help prioritize future model developments.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21R2694W
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3329 Mesoscale meteorology;
- ATMOSPHERIC PROCESSES;
- 3379 Turbulence;
- ATMOSPHERIC PROCESSES