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Radan HUTH, Monika CAH YNOVÁ Institute of Atmospheric Physics, Prague, Czech Republic

Evaluation of COST733 circulation classifications: Persistence & synoptic-climatological applicability. Radan HUTH, Monika CAH YNOVÁ Institute of Atmospheric Physics, Prague, Czech Republic. 1. Persistence (lifetime) of types. Persistence (lifetime) of types.

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Radan HUTH, Monika CAH YNOVÁ Institute of Atmospheric Physics, Prague, Czech Republic

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  1. Evaluation of COST733 circulation classifications: Persistence & synoptic-climatological applicability Radan HUTH, Monika CAHYNOVÁ Institute of Atmospheric Physics, Prague, Czech Republic

  2. 1. Persistence (lifetime) of types

  3. Persistence (lifetime) of types • length of a sequence of days classified with one type • can serve as a tool for assessing the usefulness of classifications

  4. 02 07 09 04 00 Data and methods • all COST733 classifications except Litadve • additional: OGWL with a minimum 3-day duration of CTs (…thanks to Paul James) • persistence of all types taken together • Domain 00 and 4 subdomains

  5. 02 07 09 04 00 Data and methods

  6. Basic statistics of persistence

  7. No. of days in events of given duration

  8. Conclusions • features of persistence of types are quite different among individual classifications • Erpicum’s method is probably not useful – extremely long situations occur, esp. in summer (up to 164 days!!!)

  9. 2. Synoptic-climatological evaluation

  10. GOAL • assess the synoptic-climatological applicability of classifications • i.e., how well they stratify surface weather (climate) conditions

  11. TOOL • 2-sample Kolmogorov-Smirnov test • equality of distributions of the climate element under one type against under all the other types x

  12. TOOL • at each station • types for which the K-S test rejects the equality of distributions are counted • the larger the count, the better the stratification, the better the synoptic-climatological applicability

  13. ANALYSIS • 20 objective class’s over domain 00 (whole Europe) • + 6 subjective and objectivized catalogues (not assigned to any domain) • from the v1.0 release of COST733 database • winter (DJF) • maximum temperature • 97 European stations (ECA&D database) • Jan 1958 – Feb 1993

  14. Example: Hess&Brez., 4 types

  15. Summary over types: %age of test rejections subjective + objectivized catalogues 100 % 85-99 % 70-84 % x <70 %

  16. Summary over types: %age of test rejections objective catalogues 100 % 85-99 % 70-84 % x <70 %

  17. RANKING OF CLASS’S • methods ranked by the %age of rejected K-S tests (= well separated classes) at all stations individually • higher %age  better  lower rank • ranks averaged over stations for each classification • area mean rank  ranking of the classification

  18. RANKING OF CLASS’S • dependence on no. of classes • lower number  larger class sizes  smaller difference necessary for significance  more (higher %age) of rejections  better stratification

  19. RANKING OF CLASS’S corr = 0.48

  20. PRELIMINARY CONCLUSIONS • synoptic-climatological applicability widely differs among class’s • synoptic (& objectivized) catalogues compete successfully with objective methods (although not originally designed for the large domain) • Hess-Brezowsky outperforms all objective methods with comparable no. of types

  21. FURTHER WORK FOR ME • other seasons (at least JJA) • other climate elements (Tmin, precip, …) • all domains • gridded data ( averaging over stations may not be fair)

  22. FURTHER WORK FOR WG2 • ranking is sensitive to no. of classes  sensitivity should be removed if classification methods are compared Therefore: • recalculate classifications • for other numbers of types – preferably • low (around 10) • moderate (around 20) • high (around 30) • at a selection of domains at least • CEC method (Enke&Spekat) – year-round definition of types

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