Satellite Sensors/Data Sets Summary & Recent Developments

1. Satellite Sensors/Data SetsSummary & Recent Developments

2. Satellite Sensors • TOMS (1978-2005) • BUV/SBUV/SBUV-2* (1970- cont) • OMI (7/2004- cont) • METOP/GOME-2 (2007-)* • NPP/OMPS* (2010-) * In collaboration with NOAA

3. 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 • (aerosols can be measured under cloud-free conditions, CHOCHO has been observed) • Radiation Products • Surface UV, Cloudiness index, aerosol absorption optical depth • (some info about cloud structure)

4. OMI-MLS Tropospheric Column Ozone Ziemke & Chandra

5. El Nino 2004 versus El Nino 2006 2004 2006

6. Prop const depends on plume ht 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.

7. SO2 from Jebel al-Tair Volcano in Red Sea Carn, Krueger & Krotkov Oct 1 , 2007 Oct 2 Oct 3

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

9. KEY RETRIEVAL ISSUE Sensitivity to the altitude of the center of mass of plume/gas profile

10. Sensitivity to SO2 Plume Height 50% cloud cover Assumed plume ht 7.5 km cloud ht 3.5 km Clear sky

11. Sensitivity to Aerosol Plume ht 50% cloud cover Clear sky cloud ht 3.5 km Assumed plume ht 3 km

12. Sensitivity to NO2 CM altitude 25% cloud cover Clear sky cloud ht 3.5 km CM of plume at 1 km

13. Some Recent Developments “Paradigm Shifts” • Effect of clouds on trace gas/aerosol absorption (Joiner, Vassilkov, Bhartia, Torres, Krotkov) • O3 profile from BUV sensors (Liu, Bhartia, Chance) • Effect of aerosols on UV radiation (Torres, Bhartia, Krotkov) • New methods of measuring trace gas columns from ground (Herman, Cede, Mount)

14. Clouds • Old Paradigm: • In presence of thick clouds absorption of backscattered solar radiation stops at the cloud-top level; one can use IR to estimate this height. • One needs geometrical cloud fraction (GCF) to estimate trace gas absorption. • Evolving Paradigm • One sees into the atmosphere far below the IR-derived cloud top height. • GCF is not needed for estimating trace gas absorption in UV/VIS/SWIR.

15. Clouds- as observed by CLOUDSAT, MODIS & OMI Cloudsat radar reflectivity MODIS cloud-top press is insensitive to cloud vertical structure Radiative cloud press calculated using OMI-measured Rot Raman Scattering is sensitive to cloud vert structure (ref : Vassilkov et al., JGR 2008 (accepted)

17. Mixed Cloudy/clear Scenes 50% SURFACE 50% CLOUD Reflectivity Rs=0.05 Rc=0.45 Trace gas column above Ns Nc Rmeas= 0.5Rs+0.5Rc=0.25 Nmes= 0.1Ns+ 0.9Nc

18. Impact • Deep convective clouds cannot be used to measure strat O3 column except in Pacific. • In a typical cloudy scene one sees down to ~3 km, which means high sensitivity to free trop column even in cloudy conditions. • Low sensitivity to PBL in mixed scenes, particularly in VIS & SWIR. • Cloud avoidance by going to higher spatial and/or temporal resolution is necessary for remote sensing of the PBL trace gases/aerosols.

19. O3 profile from the BUV technique • Old Paradigm: • The technique cannot be used to measure O3 profile below the O3 density peak (20-25 km), i.e., cannot be used to separate strat O3 column from total column. • Evolving Paradigm: • By adding few wavelengths (to SBUV) one can improve lower profile information well enough to estimate strat O3 column with better precision than Aura/MLS.

20. Comparison of MLS/OMI 0-215 hPa O3 Columns

21. Single Orbit Comparison

22. Longitudinal Variability

23. Impact • OMI should be able to provide strat O3 profile better than AIRS or TES. • One may not need Aura/MLS to map trop O3 column from OMI. • To do better than OMI the limb instrument must have greater precision and/or higher vert resolution in the lower strat than Aura/MLS. • GEO UV instrument should be able to measure trop O3 column well.

24. Aerosol Absorption in UV • Old paradigm: • UV measurements from space or ground cannot tell us anything new about aerosols. • Evolving Paradigm: • Most aerosols have strong UV absorption. • One may be able to separate aerosol type by comparing their absorption between blue and UV.

25. Aerosol Absorption in UV Dust OC tabs=0.05 BC

26. Measured Spectral dep of tabs Source: Krotkov et al.

27. Impact • OC/SOC aerosols may have larger impact on surface actinic flux and UVB, than are predicted by current models. • It may be possible to estimate this absorption using OMI measurements.

28. Measurement of Trop Trace Gas Column From Ground • Old Paradigm: • Multi-axis DOAS (MAX-DOAS) is the only viable way of measuring this column. • Evolving paradigm: • Direct-sun technique can provide much higher accuracy and comparable precision. Iz Ih Ih/Iz is not affected by instrument calibration, but is very sensitive to PBL trace gases. However, it is sensitive to 3-dim trace gas profile and aerosols. Iz Ih MAX-DOAS

29. Temporal Variability of NO2 at Goddard Instruments have sub-ppb level precision

30. Instrument Comparison at Table Mt , CA

31. Summary • We are learning a lot from OMI about the capabilities of the “old” BUV technique that Goddard developed in the 60s. • Clouds help in tracking transport of aerosols and trace gases in the free troposphere, but greatly hinder measurement of trace gases/aerosols in PBL. • Ground-based measurements developed in the Branch are critical for interpreting satellite data (as is the case with AERONET and MODIS). They are not just for validation. • Sondes/LIDARS are not accurate enough to validate satellite-derived strat column O3. Simultaneous measurement of total O3 by a direct-sun instrument is req’d.