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CEH-GEAR dataset (BHS2014 Birmingham)

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CEH-GEAR dataset (BHS2014 Birmingham)

  1. 1. Maliko Tanguy, V. Keller, I. Prosdocimi, J. Terry, O. Hitt, S. Cole, M. Fry, D. Morris and H. Dixon BHS 2014, Birmingham 2-4 September The new CEH-GEAR dataset: Fine resolution daily and monthly areal rainfall estimates for the UK
  2. 2. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  3. 3. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  4. 4. Introduction Method Analysis Examples Access Images from: shutterstock, clipartpanda.com What does CEH-GEAR stand for? Gridded Estimates of Areal Rainfall
  5. 5. Introduction Method Analysis Examples Access Images from: shutterstock, clipartpanda.com What is CEH-GEAR dataset? MAIN PRODUCT: 1 km gridded rainfall DAILY and MONTHLY totals for the UK 1890-2012 UPDATED YEARLY SUB-PRODUCTS: DAILY and MONTHLY grids of the distance to the closest gauge Ancillary grids: - grid of first year of missing data - grid of last year of missing data - grid of total days/months of missing data
  6. 6. Introduction Method Analysis Examples Access Hydrological purposes Long record (back to 1890) Images from: bestclipartblog.com, metoffice.gov.uk, clipartbest.com, dreamstime.com CEH-GEAR: Main Features Based on observed data FREE (terms & conditions apply)
  7. 7. 0 1000 2000 3000 4000 5000 6000 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Number of raingauges Year GB daily gauges Introduction Method Analysis Examples Access Raingauge network density varies in time. Peak in 1975: ~5000 gauges Pre-1961: few stations digitised (500 in 1960) From1961: most gauges been digitised Decrease since mid-70s: currently around 2700 raingauges
  8. 8. Introduction Method Analysis Examples Access Raingauge network density varies in time. 1910 1940 1961
  9. 9. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  10. 10. NATURAL NEIGHBOUR method Based on THIESSEN polygons Image from: ESRI Intro Methodology Analysis Examples Access Complies with BS 7843-4:2012 from the British Standards Institution
  11. 11. rci,t = calculated rainfall for point i at time interval t i rj,t = measured rainfall for raingauge j at time interval t j=1 j=2 j=3 j=… j=p Image from: Wikipedia Wi,j,t = Weight for raingauge j in time interval t, when used in the estimation of rainfall for target grid point i Si , Sj = Standard-period Average Annual Rainfall (SAAR) at point i and j Intro Methodology Analysis Examples Access Natural neighbour method
  12. 12. Normalisation by SAAR For GB: Met Office SAAR (Spackman, 1993) For Northern Ireland: Met Eireann SAAR (Walsh, 2012) Intro Methodology Analysis Examples Access
  13. 13. Intro Methodology Analysis Examples Access Monthly correction factor  daily and monthly grids consistent = Sum of daily rainfall totals for 1 month Monthly rainfall total
  14. 14. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  15. 15. Intro Method Analysis Examples Access For validation: 14 sites chosen
  16. 16. Intro Method Analysis Examples Access Sites chosen in areas with high spatial variability in rainfall
  17. 17. Intro Method Analysis Examples Access Error: Some outliers (Scotland) Larger error for bigger rainfall events On average: slightly underestimates biggest rainfall events Low rainfall High rainfall rcp: calculated rainfall rco: observed rainfall Error Small error when no or little rain
  18. 18. Intro Method Analysis Examples Access For assessing the effect of network density: 138 SEPA TBRs (Tipping bucket raingauges)
  19. 19. Intro Method Analysis Examples Access Effect of network density: Median absolute error vs. Distance to the closest gauge Low rainfall High rainfall Error  with distance for BIGGEST rainfall events Error  when distance to the closest gauge  Absolute error Distance (km)
  20. 20. Intro Method Analysis Examples Access Error  when distance to the closest gauge  MINIMUM DISTANCE GRIDS: Grid of the distance to the closest gauge
  21. 21. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  22. 22. Intro Method Analysis Examples Access Drought Monitoring Drought indicator: SPI (Standardised Precipitation Index) March 2010 June 2010 May 2011 March 2012 June 2012
  23. 23. Intro Method Analysis Examples Access Land surface model CHESS: JULES applied to the UK CEH-GEAR used as one of the 7 driving variables to run CHESS. CEH-GEAR Images from: jules.jchmr.org
  24. 24. Intro Method Analysis Examples Access Will use CEH-GEAR dataset to derive catchment averaged rainfall time series. National River Flow Archive www.ceh.ac.uk/data/nrfa/ Catchment averaged rainfall time series This data is fictitious. Used for illustration purpose. only Images from: www.ceh.ac.uk/data/nrfa/
  25. 25. Contents 1 Introduction 2 Methodology 3 Analysis 4 Examples of use 5 Access
  26. 26. Intro Method Analysis Examples Access https://gateway.ceh.ac.uk
  27. 27. Intro Method Analysis Examples Access CEH GEAR First result
  28. 28. Intro Method Analysis Examples Access Images from: http://www.narccap.ucar.edu/ Data stored in NetCDF format • array oriented scientific data • highly portable • built-in metadata
  29. 29. Intro Method Analysis Examples Access Will be fully operational in November 2014 http://doi.org/10.5285/5dc179dc-f692-49ba-9326-a6893a503f6e THREDDS DATA SERVER In the meantime: enquiries@ceh.ac.uk
  30. 30. Summary of key ideas Images from: shutterstock, clipartpanda.com UK 1km gridded rainfall DAILY and MONTHLY totals Back to 1890 and updated yearly CEH-GEAR COME AND SEE ME AT THE STAND !
  31. 31. For more info: CEH stand at BHS 2014, Birmingham Contact: maliko.tanguy@ceh.ac.uk Twitter: @MalikoTanguy @CEHScienceNews Thank you

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