MeteoSwiss - Verification

MeteoSwiss supervises many aspects of its model suites. COSMO Model output, for instance, is operationally verified against:

surface observations in Switzerland (hourly) and Europe (3-hourly) for 2 m-temperature, dewpoint, pressure (station pressure and reduced to sea level), wind (speed and direction), cloud cover, precipitation, and wind gusts.
upper air data from radiosonde ascents for temperature, wind, geopotential and humidity
radar data for precipitation
windprofiler data and flux measurements in Payerne for different near-surface and boundary layer parameters (short and longwave surface radiation, albedo, sensible and latent heat flux).

For COSMO verification results of the past years, refer to the COSMO Newsletters.

Main results

Percentage of correct forecasts of 2m-temperature within 2, 5, 8 degrees C in Spring 2005 over Switzerland for gridpoints < 800 m. COSMO direct model output (black line), COSMO output adjusted with Kalman filter (red line).

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Surface observations:

2m-temperature: With the Kalman-filter correction, 75% of all hourly forecasts show an error of < 2 degrees C for the first day of the forecast dropping to a high 65% for day 3 (left, top). During the evening and at nighttime, there is a cold bias (especially in winter). The amplitude of the diurnal cycle is too large and the maximum about 1.5 hours too early (left, bottom).
2m-dewpoint: The diurnal cycle ist not well captured, but the Kalman filter corrects the systematic biases.
10m-wind: The wind speed is overestimated (especially during nighttime). For mountain gridpoints there is a strong underestimation (due to the same parameterization of the boundary layer over flat and complex topography).
precipitation: The low amounts (0.1 mm in 6 hours) are overestimated. In summer the mean diurnal cycle of convective precipitation has its maximum about 4 hours too early.

Verification of the 2m-temperature diurnal cycle in Spring 2005 over Switzerland for gridpoints < 800 m. Observations (ANETZ, thin black line), COSMO direct model output (dashed black line), COSMO output adjusted with Kalman filter (dotted red line).

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Vertical profiles:

There is a cold bias from the surface up to 750 hPa (mainly in summer). The mean error in wind speed is small, with a positive bias in the boundary layer (at least during the cold season) and a small negative bias above 800 hPa.

Verification of COSMO forecasts

Main results

Surface observations:

Vertical profiles: