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Introduction

Short-term, platform-like inhomogeneities in observed climatic time series Peter Domonkos Centre for Climate Change University Rovira i Virgili, Tortosa, Spain. Introduction.

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Introduction

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  1. Short-term, platform-like inhomogeneities in observed climatic time seriesPeter DomonkosCentre for Climate ChangeUniversity Rovira i Virgili, Tortosa,Spain

  2. Introduction • Series of experiments show that observed climatic time series usually contain large number of platform-like inhomogeneities (IHs). These IHs mostly have short durations and relatively small magnitudes, therefore their direct detection is usually impossible. They act as a special kind of noise when the homogenizer is looking for large, persistent IHs. • Platform-like IHs have considerable impact on the IH-detection results.

  3. Connection between real and detected IHs: 5 shifts per 100 years

  4. Connection between real and detected IHs: 5 platforms per 100 years

  5. Standard Dataset: Statistical properties of detected IHs are similar to the ones detected in real temperature time series

  6. Large number of small, platform-like IHs: Why? • Observation-errors often persist only for limited time, because they are eliminated after their realisation. • Changes in climatic gradients • IHs in the components of reference series • Anything is their origination: they exist when homogenizers work.

  7. Statistics of detection frequency IH(all) = all the IHs detected with ACMANT IH(S) = IHs detected with the Secondary detection The frequency of short-term IHs is lower in the simulated datasets than in the observed datasets.

  8. 1 break per time-series (100 years), M = 3.5σ

  9. 5 breaks per 100 years, Mmean= 3.5

  10. 5 platforms per 100 years, Mmean= 3.5

  11. Standard Dataset

  12. 5 platforms per 100 years, Mmean= 1

  13. Frequency of detecting at least one IH per time series

  14. Conclusions • Small, platform-like IHs occur with large frequency in observed climatic time series. • The presence of small, platform-like IHs changes the performance of homogenisation methods, therefore they should be present also in simulated datasets for testing the efficiencies of homogenisation methods.

  15. Thank you for your attention!

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