The COST Action 733 “Harmonisation and Applications of Weather Type Classifications for European Regions” is a coordinated effort to develop, compare and apply numerical methods for the objective classification of weather situations in European regions.
Currently, participants from 21 European countries collaborate within COST 733. Swiss participants are the University of Berne (Institute of Geography) and MeteoSwiss. For more details see http://www.cost733.org
The objectives of MeteoSwiss within COST 733 are:
- To identify automatic classification methods that could complement or substitute manual schemes currently in use at MeteoSwiss. To this end, various schemes are compared with respect to their discrimination in surface climate variations. In these analyses, particular emphasis is put on the distribution of precipitation in the Alps (Figure 1).
- To examine if and how weather type information could be exploited as supplementary real-time information for spatial precipitation analysis. These studies seek to improve current real-time analyses based solely on the scarce network of automatic rain-gauges. (Figure 2).
Figure 1. (a) Composites of sea-level pressure, precipitation, and 2m-temperature anomaly for weather type '2' of the PCACA classification[1] (graphics Paul James, COST 733). (b) Probability of precipitation occurrence on days with the weather type shown in (a), divided by the climatological probability. (c) The same for the probability of exceeding the 95% quantile.
Figure 2. Precipitation grids for Switzerland on March 13, 2004 (mm/d). (left) Gridding with a reference method (SYMAP, [2]), (centre) gridding by means of reduced-space optimal interpolation[3], (right) grid obtained from the full high-resolution gauge network[2].
References
[1] PCACA weather type classification by Domingo Rasilla, Universidad de Cantabria, Departamento de Geografía, Spain. [2] Frei, C. and C. Schär, 1998: A precipitation climatology of the Alps from high-resolution rain-gauge observations. Int. J. Climatol., 18, 873-900.
[3] Schiemann, R. and C. Frei, 2008: Alpine mesoscale precipitation variability and weather types – Exploring the value of weather types classifications for precipitation gridding.
presented at the workshop “Variability of the Global Atmospheric Circulation during the Past 100 Years”, Monte Verità, Switzerland, June 15-20, 2008.
For further information, please contact: Reinhard Schiemann and Christoph Frei.
