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Jim Haywood, Ben Johnson, Andy Wilson, Martyn Pickering, Stuart Rogers, Dave Tiddeman (OBR)

The Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave radiation (GERBILS). Jim Haywood, Ben Johnson, Andy Wilson, Martyn Pickering, Stuart Rogers, Dave Tiddeman (OBR) Sean Milton, Malcolm Brooks, Glenn Greed (GMDD) Mark Harrison (Atmos. Dispersion)

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Jim Haywood, Ben Johnson, Andy Wilson, Martyn Pickering, Stuart Rogers, Dave Tiddeman (OBR)

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  1. The Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave radiation (GERBILS) Jim Haywood, Ben Johnson, Andy Wilson, Martyn Pickering, Stuart Rogers, Dave Tiddeman (OBR) Sean Milton, Malcolm Brooks, Glenn Greed (GMDD) Mark Harrison (Atmos. Dispersion) Marie Doutriaux-Boucher, Joanne Crawford (SDPS) Met Office, UK Tony Slingo, Richard Allan, Gary Robinson ESSC, Reading University

  2. Objectives: • To quantitatively assess the effect of mineral dust on the Earth radiation budget (solar and terrestrial wavelengths). • To assess the errors in the global numerical weather prediction model owing to the lack of inclusion of mineral dust. • To assess the performance of the dust scheme within the CAMM. • To validate satellite retrievals of • GERB • SEVIRI • TOMS • MODIS (deep blue) • MISR

  3. The inter-annual variability of clear-sky DOLR. Red/orange colours indicate that the model OLR is too high by approximately 40-50Wm-2. UM – GERB (cloud-free): Light blue = no differnce Red = Model emits 50Wm-2 too much OLR

  4. Statistics indicating the probability of obtaining a cloud free day and a significant dOLR (for six flights):

  5. The BAe146 is booked for provisional flying from Niamey to Nouakchott:-

  6. Flight plan for GERBIL: GERB Intercomparison of Longwave and Shortwave radiation GERB/SEVIRI

  7. Satellite retrievals of the dust during GERBILS:

  8. More detail of the TOMS images: Flight Date: 19th 20th 21st 22nd 23rd 24th 25th 26th 27th 28th Nouakchott Niamey

  9. Polar orbiting satellite vs Geostationary satellites • All polar orbiting satellites have their limitations as the coverage is once a day. • Geostationary satellites (e.g. Meteosat 8 (MSG-2nd genration), Meteosat 9) • GERB (Geostationary Earth Radiation Budget) makes broadband solar and terrestrial at ~15minute resolution. • SEVIRI (Spinning Enhanced Visible and Infra-Red Imager) 12-channel imager including 10.8mm and 12mm bands.

  10. The terrestrial radiative effect is also significant. C-130 measurements using ARIES (cm-1 resolution interferometer) clearly show the effect of Saharan dust in the 8-12mm atmospheric window. 12mm 10.8mm Positive slope = no aerosol Negative slope = aerosol Dusty Clear Nadir views from 18,000ft (R6) (above aerosol). Measured surface temperature (from 100ft) 302.5K

  11. SEVIRI images every 1hour (can get every 15mins): Nouakchott Niamey

  12. Another primary objective is to validate the dust model within the CAMM: CAMM was used as a forecast tool.

  13. Cross sections available at every 2.5degrees latitude:

  14. Transit Flight: 18th June

  15. ‘Standard Flight’ 19th June

  16. ‘Non-Standard Flight’ 21st June

  17. ‘Very non-standard Flight: 22nd June’

  18. ‘Recovery Flight: 22nd June’

  19. 4 more ‘standard flights’ performed and 1 scientific transit back to Marrakesh.The standard flight pattern means that the surface characteristics (albedo, temperature, emissivity) can be well determined.

  20. VERY preliminary science results:

  21. TOMS AOD over the period:

  22. deltaOLRc over the period:

  23. TOMS and dOLRc over the period: Bias of 20 of Wm-2 is what we’d expect (statistically)

  24. Transit Flight:

  25. Looking at the upwelling SOLAR radiation over ocean: Dust aerosol appears at 22.5N and shows a strong gradient to 20N 100Wm-2 – 50Wm-2 -> direct radiative effect of the dust over ocean is 50Wm-2. RT modelling suggests AOD=0.52 at 0.55mm ~50Wm-2 is what RT modelling suggests we should have over oceans

  26. CAMM model gets the dust in the right place, the magnitude may be slightly low (more investigation required ). 22.5N 20N 10N

  27. The dust was moving quickly: to the south of the 18N line of latitude. Satcom was used to give update using SEVIRI. Dakar Cinzana Model does predicts high optical depths >3, but some of the details are wrong.

  28. AERONET from CINZANA, Mali Dakar shows good agreement, but Cinzana does not. AERONET from Dakar, Senegal

  29. Summary: • 2 transits: 1 very successful (1 dusty) • 5 standard flights concentrating on 18oN (4 dusty). • 2 non-standard flights (2 dusty) • 1 recovery flight (no dust and cloudy) Success rate 7/10 – very good considering the statistics (plus we wanted a non-dusty case anyway).

  30. PS) It was dusty, but not THIS dusty (from Niamey, 7th July):-

  31. PS) It was dusty, but not THIS dusty (from Niamey, 7th July):-

  32. PS) It was dusty, but not THIS dusty (from Niamey, 7th July):-

  33. PS) It was dusty, but not THIS dusty (from Niamey, 7th July):-

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