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Lessons Learned From Aura/OMI- Implications for TROPOMI

Lessons Learned From Aura/OMI- Implications for TROPOMI. Pawan K. Bhartia Laboratory for Atmospheres NASA Goddard Space Flight Center Maryland, USA. OMI Data Sets. Stratospheric products O 3 column & profile

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Lessons Learned From Aura/OMI- Implications for TROPOMI

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  1. Lessons Learned From Aura/OMI- Implications for TROPOMI Pawan K. Bhartia Laboratory for Atmospheres NASA Goddard Space Flight Center Maryland, USA

  2. OMI Data Sets • Stratospheric products • O3 column & profile • (BrO column and OClO slant columns are being produced but have not been extensively studied) • Free-Tropospheric products • Trop O3, Aerosol Index, volcanic SO2 • (lightning NO2 and pollution SO2 have been observed) • PBL products • NO2, HCHO, BrO • (aerosols can be measured under cloud-free conditions, CHOCHO has been observed) • Climate & Radiation Products • Radiative cloud fraction (an index of cloudiness) • Aerosol absorption optical depth • Radiative cloud pressure (sensitive to cloud structure) • Surface UV

  3. Tropospheric Ozone from OMI-MLS MLS/OMI tropospheric ozone – monthly average July and October 2005,Ziemke et al., JGR 2006 24 and 28 June 2005 Global maps of tropospheric ozone showing effects of pollution in the Northern Hemisphere in summer and biomass burning in Southern Hemisphere in spring Ozone pollution from North America to Europe or stratospheric ozone from a tropopause fold?

  4. Deseasonalized Time Series S.E. Pacific Tropical North Atlantic Costa Rica Eastern Africa Indonesia Western Australia

  5. OMI: SO2 emissions from smelters and volcanoes Ecuador/S. Colombia volcanoes Average OMI SO2 vertical column Sep 2004 - June 2005 Ilo copper smelter Colombia Equador La Oroya copper smelter Peru Daily SO2 burdens for 3 source regions Sept. 2004 - June 2005 La Oroya • • Daily monitoring of SO2 emissions is possible with OMI. • The Peruvian copper smelters are among the world’s largest industrial point sources of SO2. Ilo Carn et al., in prep

  6. Average (2005-2006) SO2 burdens over USA, Europe and China East-Aire’05 experiment 25.5 million tons of SO2 was emitted by Chinese factories in 2005 up 27% from 2000

  7. Lessons Learned (1) • Total column ozone can be estimated with ~1% accuracy & 0.3% precision in clear areas and in large fraction of cloudy areas. • Stratospheric ozone column can also be estimated with similar accuracy & precision when the tropopause is relatively high (>10 km). • Such performance is needed for trop O3 studies. • Requires very good instrument performance between 300-320 nm. • OMI performance is much better than GOME but still not optimal due to calibration and spectral straylight problems.

  8. Radiometric + Straylight Error Estimated Using MLS UV1 UV2 X- track Stray light? One day of MLS ZM O3 profile from tropics LLM climatology below 115 hPa Semi- analytical Ring corrn Low reflectivity data only

  9. OMI- MLS O3 Column Comparisons

  10. Impact of calibration error on trop O3 retrieval No Correction With MLS-derived Radiance Correction Accurate radiance calibration is critical for tropospheric ozone retrievals.

  11. Implications for TROPOMI (1) • The instrument needs to be optimized for better performance, particularly for straylight, in the 300-320 nm wavelength region. • The detectors shouldn’t be split at 310 nm, as is the case with OMI.

  12. Lessons Learned (2) • Effects of clouds on reflected wavelengths are very different than at thermal IR wavelengths. • Multi-layer and multi-phase clouds (mixed ice and water clouds) are far more common than previously believed, and they have significant effect on trace gas and aerosol absorption. • Knowledge of geometrical cloud fraction may not be necessary or useful for the estimation trace gas and aerosol absorption from reflected sunlight instruments, since measured reflectances apparently contain all the necessary information.

  13. Clouds as seen by CloudSat, MODIR-TIR channels and OMI Cloudsat radar reflectivity MODIS cloud-top press For well-mixed gases use of OMI-derived cloud pressure provides the correct column amount. Cloud press calculated using OMI-measured Rot Raman Scattering. (O2-O2 absorption results from KNMI are similar.)

  14. Validation of OMI’s Cloud Fraction Model Method: r340/r380 is affected primarily by cloud fraction, cloud optical depth, aerosols, and surface albedo, but not by cloud structure/height. Nimbus-7 TOMS data from the Pacific (March 20, 1979) meas calc Sea-glint

  15. Implications for TROPOMI (2) • Multi-phase and multi-layer clouds can be reliably detected by combining reflected sunlight (Raman, O2-O2 or O2 A-band) with thermal emission measurements. • Detection of such clouds is important for estimating trace gas and aerosol absorption in presence of clouds. • Such clouds may affect surface radiation by increasing absorption by trace gases and aerosols due to multiple scattering. • Detection of such clouds is important for climate studies.

  16. Lessons Learned (3) • Aerosol (extinction) optical thickness (AOT) is very difficult to measure from OMI due to sub-pixel cloud contamination, except in arid areas. • Most aerosols have very strong absorption in the UV. • Primary aerosol products from OMI are aerosol index (AI) and aerosol absorption optical depth (AAOT). • AI is very useful for tracking smoke and dust aerosols over long-distances, since the method works even when aerosol plumes go over clouds and snow/ice. • Aerosol height (center of mass altitude) is a critical parameter for the estimation of AAOT. • It may be possible to measure AAOT over clouds and snow/ice.

  17. Aerosol Absorption increases in UV Dust OC tabs=0.05 BC

  18. Aerosol Index Smoke Desert Dust Smoke from Colorado fires (June 25, 2002) Transport of Mongolian dust to N. America in April 2001. This image was made by compositing several days of TOMS data.

  19. Detection of Smoke over Clouds

  20. Effect of smoke over clouds on TOA radiation SeaWiFS True Color CERES short-wave flux 21 April 2001 TOMS Aerosol Index DFTOA = FTOA(CLD)- FTOA(CLD/SMK) = ~200 Watts m-2

  21. Implications for TROPOMI (3) • Possible use of O2 A-band for the estimation of aerosol height (center of mass altitude) need to investigated. • The focus of aerosol research from OMI/TROPOMI should be on understanding the effects of absorbing aerosols on surface radiation and clouds, and not on duplicating what high resolution visible sensors, such as MODIS & MISR, do much better.

  22. SUMMARY • Trop O3 studies require very good instrument performance in the 300-315 nm range. • Combination of UV/VIS cloud information with thermal information can benefit climate studies by detecting multi-layer/multi-phase clouds . • Estimation of aerosol absorption from the UV/blue technique may greatly improve by adding O2 A-band to TROPOMI.

  23. Tropospheric Equivalent Mixing Ratio 5-day average Ziemke et al. 2006 80 0 ppbv Schoeberl et al., 2007 The high ozone feature off the east coast appears to be a fold - white contours show the tropopause gradient - not pollution. However, the magnitude of the fold tropospheric ozone event is very high….

  24. NO2 over India and Asia Gleason et al. March 2006 May 2006 July 2006 September 2006

  25. OMI CH2O (Formaldehyde) From Kurosu & Chance Offshore CH2O? VOCs emitted by forests under stress CH2O is an indicator of VOC emission, which in combination with NOx cause O3 pollution

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