U.K. Ozone and UV Trends and Extreme Events

Transcription

1 U.K. Ozone and UV Trends and Extreme Events Andrew C. Moss, Andrew R.D. Smedley and John S. Rimmer University of Manchester Acknowledgements: UKMO, DEFRA Workshop, Beijing 211

2 Introduction Overview of Sites Long term Trends in Ozone and UV Statistical Determination of Extreme Events Extreme Events Determined for: Lerwick Manchester Reading Comparison with Satellite Records Workshop, Beijing 211

3 Overview and Map of Sites 6 o N 57 o N 54 o N 51 o N 48 o N 12 o W 9 o W 6 o W Lerwick Manchester Reading Camborne 3 o W o 3 o E Lerwick: Dobson since 1952 Manchester: Brewer Mk III since 2 Reading: Brewer Mk IV since 22 Camborne: Dobson Dobson Bracknell: Dobson Workshop, Beijing 211

4 Ground Based Trends A.R.D. Smedley et al. International Journal of Climatology DOI: 1.12/joc.2275, 21 Workshop, Beijing 211

5 : Lerwick ozone: 5.8% per decade. Southern England ozone: 4.8% per decade. Decreases at upper end of range in comparison with other European stations : both sites show small increase but not statistically significant. Latest re analysis increase becomes statistically significant. Workshop, Beijing 211

6 Satellite Trends A.R.D. Smedley et al. International Journal of Climatology DOI: 1.12/joc.2275, 21 Workshop, Beijing 211

7 UV Ratio Trends Reading A.R.D. Smedley et al. International Journal of Climatology DOI: 1.12/joc.2275, 21 Workshop, Beijing 211

8 Determination of Extreme Events 5 45 EHO (blue), ELO (green) and Means (red) for each month at Reading, Thresholds found from the General Pareto Distribution. EHO Threshold ELO Threshold Means Total Ozone [DU] Month Workshop, Beijing 211

9 Gaussian Quantile Quantile Plot: Case for Changing Statistical Analysis for Identification of Extreme Events Workshop, Beijing 211

10 Extreme Value Theory Generalized Pareto Distribution Extreme events in total ozone over Arosa: Part 1: Application of Extreme Value Theory. Rieder et al. Atmos Chem Phys, 1, 121, 21 Extreme events in total ozone over Arosa: Part 2: Fingerprints of atmospheric dynamics and chemistry and effects on mean values and long term change. Rieder et al.. Atmos Chem Phys, 1, 133, 21 Workshop, Beijing 211

11 Determination of Threshold Fit the GPD model to the data for a range of thresholds. Find the point where the shape parameter becomes constant. Check that this threshold does actually provide the best fit. Workshop, Beijing 211

12 Quantile Quantile Comparison Workshop, Beijing 211

13 Quantile Quantile Comparison Workshop, Beijing 211

14 4 Seasonal Fractions of Extreme High (blue) and Extreme Low (green) O 3 Events for Lerwick, Daily Thresholds found by Interpolating between monthly thresholds found using EVT Spring % Freq Summer % Freq Autumn % Freq Winter % Freq Year Workshop, Beijing 211

15 2 Seasonal Fractions of Extreme High (blue) and Extreme Low (green) O 3 Events for Reading, Daily Thresholds found by Interpolating between monthly thresholds found using EVT Spring % Freq Summer % Freq Autumn % Freq Winter % Freq Year Workshop, Beijing 211

16 3 Seasonal Fractions of Extreme High (blue) and Extreme Low (green) O 3 Events for Lerwick Satellite Data, Daily Thresholds found by Interpolating between monthly thresholds found using EVT 2 Spring % Freq Summer % Freq Autumn % Freq Winter % Freq Year Workshop, Beijing 211

17 6 Seasonal Fractions of Extreme High (blue) and Extreme Low (green) O 3 Events for Reading Satellite Data, Daily Thresholds found by Interpolating between monthly thresholds found using EVT Spring % Freq Summer % Freq Autumn % Freq Winter % Freq Year Workshop, Beijing 211

18 4 Seasonal Fractions of Extreme High (blue) and Extreme Low (green) O 3 Events for Manchester Satellite Data, Daily Thresholds found by Interpolating between monthly thresholds found using EVT Spring % Freq Summer % Freq Autumn % Freq Winter % Freq Year Workshop, Beijing 211

19 25 Annual Fractions Reading Ground Based Data, Annual % Freq Annual Fractions Reading Satellite Data, Annual % Freq Year Workshop, Beijing 211

20 3 Annual Fractions Lerwick Ground Based Data, % Frequency of Extreme High (blue) and Low (green) O 3 Events Year Annual Fractions Lerwick Satellite Data, Year Workshop, Beijing 211

21 5 Lerwick ( ) Ground Based and Satellite Ozone Data Monthly Extreme Value Thresholds found using the General Pareto Distribution and Monthly Mean Values. Lerwick 197 Ground Based Means Lerwick 197 Ground Based EVT Extreme High Thresholds Lerwick 197 Ground Based EVT Extreme Low Thresholds 45 Lerwick 197 Satellite EVT Extreme High Thresholds Lerwick 197 Satellite EVT Extreme Low Thresholds Lerwick 197 Satellite Means 4 Total O 3 [DU] Month Workshop, Beijing 211

22 Conclusions Tentative signs of ozone recovery. Ozone inadequately described by a Gaussian Distribution EVT fits the extreme tails much better and provides different thresholds Frequency of extreme events follows overall trend of data as you would expect Seasonal Frequency loosely follows the same trend generally, however, variations from season to season Significant difference between extreme event frequency between Lerwick Dobson and satellite. Difference in thresholds. Workshop, Beijing 211

23 Thank You! Workshop, Beijing 211