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