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Comparison of GERB and Met Office UM Broadband Fluxes: SINERGEE Project Results

This study compares broadband fluxes from GERB and Met Office UM, analyzing data issues and model limitations. Recent comparisons and examples are provided, highlighting geolocation and albedo biases. The study addresses issues such as desert dust, aerosols, and spatial coverage, offering conclusions on data and model problems.

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Comparison of GERB and Met Office UM Broadband Fluxes: SINERGEE Project Results

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  1. Comparison of GERB and Met Office UM broadband fluxes: SINERGEE project results Richard Allan, Tony Slingo ESSC, Reading University

  2. INTRODUCTION • - SINERGEE aims • Comparison of GERB L2 broadband fluxes with Met Office forecast model (analysis times 00,06,12,18 GMT) • July Means, Clear-sky sampling • Data issues (geolocation, resolution, bad data, ADMs) • Model Issues (Sahara, convection, cloud properties)

  3. Recent Comparison (OLR)

  4. Recent Comparison (Albedo)

  5. Example Comparion (OLR)

  6. Example Comparion (Albedo) Stratocumulus Convection Geolocation

  7. UM GERB July Mean OLR

  8. Limb effects?? GERB-UM OLR DifferenceJuly Mean

  9. GERB Consistently sampled clear-sky “Type-I” OLRJuly UM

  10. Clear-sky OLR bias with TsGERB minus UM OLR (Wm-2) 30 20 10 0 -10 -20 -30 -40 -50 -60 280 300 320 340 SURFACE TEMPERATURE (K)

  11. Desert Dust? Aerosol?

  12. July Mean Albedo (GERB) 06z

  13. July Mean Albedo (UM) 06z

  14. GERB GeolocationMean clear-sky albedoJuly UM

  15. 23rd JulyGeo-location (2): Albedo11th August

  16. Time series (diurnal cycle removed) May June July Aug Reduced spatial coverage amplifies 06z Albedo bias

  17. Light stripe (~25N or 25 S): 06z late May and 11-14th June, 12z 24-29th May Dark Band, 12z: 1-3rd, 5th June; 18z 12th June; 12z 31st July, 1st and 5th Aug OTHER ISSUES Vertical dark stripe: 06z 20th May; 12z 4th June; 00z&18z 10th June; 00z 26th, 27th & 30th June; 18z 30th June/1st July; 00z 2nd/3rd July 22nd June & 10th Aug also dodgy Bad Pixel.

  18. 10th August 12z: GERB couldn’t cope with record UK temperature of 38oC!

  19. August OLR Animation

  20. Conclusions (1) • DATA problems • Geolocation (spatial comparison, processing) • Resolution • Albedo diurnal cycle (problems at 06z) • Limb darkening in East? (Lower OLR and Higher albedo) • Meteosat data replacement = Bad • Model problems • Too much stratocumulus • 12z Convection (too early, lack of organisation) • Dark Sahara / Hot Sahara • ITCZ positioning

  21. Conclusions (2) • Quality of BARG improved recently (August) • ARG - reasonable quality (res/geo probs) • ADMs? – bright at 06z, dark at 18z • Bad data (manual correction?): • Geolocation • light stripes, dark bands (E/W) • Dark bands (N/S) • Future comparison of SEVIRI with UM simulations • http://www.nerc-essc.ac.uk/~rpa/GERB/gerb.html

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