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Data collation for the ENSEMBLES grid
Lisette KlokKNMI
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
http://eca.knmi.nl Gridded datasets (in 2007):
http://www.ensembles-eu.org/
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 values2. outliers3. inconsistencies4. 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
Useful Doubtful
Suspect Unknown
Precipitation 40% 8% 12% 40%
Temperature 35% 8% 40% 17%
…more about data quality by Evelyn Zenklusen
Homogeneity - inhomogeneity
200019801960194019201900
mD
TR
(de
gr. C
elsi
us)
13
12
11
10
9
8
7
6
5
Mean tem
perature (degr. Celsius)
11
10
9
8
7
6
5
4
3
1948: change of observation hut
1951: relocation
1959: change in sensor height
Annual mean temperature and DTR, Groningen (NL)
Homogeneity – preliminary results
Useful Doubtful
Suspect Unknown
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 dtr3. 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