Use of high-density observations in precipitation verification

Haiden, Thomas ; Duffy, Sinéad

Année de publication
2016
Résumé
Verification of forecasts against surface observations from SYNOP stations is an important part of monitoring progress in numerical weather prediction systems such as ECMWF’s Integrated Forecasting System (IFS). Parameters observed at such stations typically include 2-metre temperature and humidity, 10-metre wind, total cloud cover and precipitation. In addition to SYNOP observations, which are distributed via the Global Telecommunication System (GTS), many countries maintain higher-density national observational networks which provide data that is not generally available on the GTS. In 2014 ECMWF started an initiative to collect such observations from its Member and Co-operating States for use in model evaluation. Based on the experience gained in previous efforts (Csima & Ghelli, 2008), it was decided to use a unified data format for the data transfer in order to facilitate its long-term maintenance. Data from additional stations improves the sampling of the quantity to be evaluated. First results obtained from the use of precipitation data in forecast evaluation show that this leads to reduced noise in time series of forecast skill. It also increases confidence in comparisons between operational and experimental model cycles, which are necessarily based on a limited verification period. In the case of precipitation and wind, the fact that less frequent, higher-intensity events are of special interest adds to the value of a dense observation network.

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