Data collation for the ENSEMBLES grid Lisette Klok KNMI EU-FP6 project: Ensemble-based predictions of climate changes and their impacts

Project aim – ENSEMBLES work package 5.1 Development of daily high-resolution gridded observational datasets for Europe

Overview Background Daily series Quality Control/Homogeneity

Background – on gridded datasets Spatial domain: daily values Tmax, Tmin, P, slp, snowcover 25 km >45 years

1. KNMI, Albert Klein Tank & Lisette Klok 2. MeteoSwiss, Evelyn Zenklusen & Michael Begert 3. University of East Anglia, Malcolm Haylock & Phil Jones 4. University of Oxford, Mark New & Nynke Hofstra Background – on project partners

Background – on data availability Daily time series (if public!): website of European Climate Assessment & Dataset Gridded datasets (in 2007):

Daily series – data sources ECA&D (~409 stations) EMULATE (~78 stations) STARDEX (~236 stations) GCOS Surface Network (~48 stations) Global Historical Climate Network (~645 stations) MAP project (~110) SYNOP data for updating the series Current status: ~1526 stations

Daily series – station density ECA&D coverage 2004

Daily series – number of precipitation series

Daily series – number of max temperature series

Daily series – number of air pressure series

Daily series – number of snow depth series

Quality Control – as in ECA&D 1. anomalous values 2. outliers 3. inconsistencies 4. repetitiveness

Homogeneity – example of an inhomogeneity

Homogeneity – tests as in ECA&D Wijngaard et al., 2003 Temperature and precipitation Absolute test Classification: useful, doubtful, suspect

Homogeneity – preliminary results UsefulDoubtfulSuspectUnknown Precipitation40%8%12%40% Temperature35%8%40%17%

… more about data quality by Evelyn Zenklusen

Homogeneity - inhomogeneity 1948: change of observation hut 1951: relocation 1959: change in sensor height Annual mean temperature and DTR, Groningen (NL)

Homogeneity – preliminary results UsefulDoubtfulSuspectUnknown Snow*87%2%7%4% Air pressure*38%18%16%28% * Indices snow day count (sd > 0) annual mean air pressure

Homogeneity - Wijngaard et al., 2003 Three testing variables: 1. annual mean of daily temperature range (dtr) 2. annual mean of absolute day-to-day differences of dtr 3. wet day count (> 1 mm) Four test methods: (1) Standard normal homogeneity test, (2) Buishand range test, (3) Pettit test, (4) Von Neumann ratio test Classification: useful, doubtful, suspect depending on number of tests rejecting the null hypothesis (respectively 0-1,2,3)

Extra Number of series rr: 1597 tx: 1089 tn: 1088 pp: 258 sd: 129 Air pressure series: 21% does not show a trend at 5% level