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Assessing the impact of synoptic-scale dynamics and processes on the quality and predictability of quantitative precipitation forecasts over Switzerland

English title Assessing the impact of synoptic-scale dynamics and processes on the quality and predictability of quantitative precipitation forecasts over Switzerland
Applicant Davies Huw Cathan
Number 105591
Funding scheme Project funding (Div. I-III)
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Meteorology
Start/End 01.03.2005 - 29.02.2008
Approved amount 125'296.65
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Keywords (6)

synoptic meteorology and dynamics; radar meteorology; precipitation analysis; statistics and numerical modelling; precipitation forecasting; verification

Lay Summary (English)

Lead
Lay summary
A high-resolution observational data set, consisting of a daily Swiss rain gauge climatology disaggregated by hourly radar data, is the basis for a systematic error analysis of precipitation forecasts and analyses from the operational mesoscale model of MeteoSwiss. The application and development of conventional and novel error measures and the performance of a conditional verification (taking into account ambient flow and thermal conditions) results in the first long-term error climatology for QPF over Switzerland. The results comprise: -Overestimation over high terrain, underestimation in Alpine valleys and the Mittelland. Potential improvements include the prognostic precipitation scheme. -Distinct differences in error climatology for different weather classes. This indicates the importance of the accuracy of the boundary data for mesoscale models. -Underestimation of small and medium-intensity events, overestimation of heavy precipitation events. An exception is the Ticino, where there are strong seasonal differences and an underestimation of high intensities in spring. This points to specific physical processes and dynamical interactions that prevail on the southern side of the Alps in this season. -Differences between analysis and observations also carry an orographic signal, hence are deteriorated by model deficiencies. -In summer the daily cycle shows significant problems. The main precipitation peak occurs ~2h early in the model.
Direct link to Lay Summary Last update: 21.02.2013

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