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European Climate Assessment & Dataset Judging homogeneity of daily series

European Climate Assessment & Dataset Judging homogeneity of daily series. Fourth seminar for homogenization Budapest, 6-10 October 2003. Janet Wijngaard, KNMI, the Netherlands. Topics. ECA&D project Approach to homogeneity Results, Conclusions. ECA&D project.

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European Climate Assessment & Dataset Judging homogeneity of daily series

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  1. European Climate Assessment & Dataset Judging homogeneity of daily series Fourth seminar for homogenization Budapest, 6-10 October 2003 Janet Wijngaard, KNMI, the Netherlands

  2. Topics • ECA&D project • Approach to homogeneity • Results, Conclusions

  3. ECA&D project • data analysis focusing on observed changes in extremes • gather daily series of observations at meteorological stations in • Europe and the Middle East • quality control and homogeneity analysis of the series • dissemination of data and analyses results

  4. Current participation • Most data from 1900 up to 2001 • More than 200 stations • Tmin, Tmax, Tmean, • precipitation amount, pressure

  5. Trend analysis of extremes requires: A dense, high-resolution, accurate and consistent dataset

  6. Method Homogenization of daily series Instead: labelling of series -> confidence for trend and variability analysis

  7. Two-step approach • Four homogeneity tests applied to ECA dataset to identify potential inhomogeneities in annual resolution testing variables representative for the daily resolution • Grouping of results -> overall classification

  8. Homogeneity tests and variables • Tests (absolute): • SNHT • Buishand Range • Pettitt • Von Neumann Ratio • Variables: • precipitation: number of wet days • temperature: mDTR and vDTR (annual mean of absolute day-to-day • differences of DTR)

  9. vDTR DTRi:Diurnal temperature Range for day i in a specific year M: number of days in the year

  10. Classification • Labels: • Useful (0/1 tests significant) • Doubtful (2 tests significant) • Suspect (3/4 tests significant)

  11. Station Groningen (NL) 1948: change of observation hut 1951: relocation 1959: change in sensor height

  12. Station Groningen (NL) Buishand Range, Pettitt and Von Neumann significant -> ‘suspect’

  13. Temperature 1946-1999 mDTR vDTR ->54% ‘suspect’, breaks (partly) supported by metadata

  14. Precipitation 1946-1999 Number of wet days Paper: International Journal of Climatology, May, 2003 -> 10% ‘suspect’

  15. Conclusions • most severe step-wise breaks are detected • metadata support for detected breaks essential • no homogenizing of daily series • labelling system good basis for series selection in trend analysis

  16. And… • further investigations to test homogeneity on daily basis • MASH method used for homogenization on monthly ECA&D series

  17. More info at: http://www.knmi.nl/samenw/eca

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