1. Satellite Observations of Tropospheric Aerosols: More than Pretty Pictures Symposium in Honour of Jennifer Logan, Harvard University May 10, 2013 Colette L. Heald Maria Val Martin, Bonne Ford, David Ridley Let’s not forget: an institution that trained Jennifer Logan!

2. Challenge: Heterogeneity of Atmospheric Aerosols GEOS-5 10 km aerosol model http://www.nasa.gov/multimedia/imagegallery/image_feature_2393.html Many first order problems in aerosols (how much? what sources?) challenging to address because of the short lifetimes and varying properties of particles in the atmosphere.

3. Solution: Satellites! 1. Identify air masses 2. Context (spatial and temporal) 3. Track (investigate processing) 4. Identify sources 5. Constrain Budgets

4. Transpacific Transport of Asian Aerosol Pollution as Seen by MODIS April 25, 2001 April 26, 2001 April 27, 2001 Most basic use of satellite observations (Identify events) MODIS AOD GEOS-Chem dust AOD GEOS-Chem Asian sulfate AOD [Heald et al., 2006]

5. Satellite Measurements Show How High Aerosol Loading (AOD) is Associated with Both Local and Transported Smoke June 2002 [val Martin et al., submitted] MODIS Terra AOD anomalies August 2012 Hayman Fire High Park and Waldo Fires AZ Wallow Fire (2011) MT, WY, ID, WA Fires AZ, CA Fires CA Station Fire (2009) Continuous satellite observations can integrate across events and regions (Context)

6. Dust From North Africa: Using Satellite Observations to Test Sources, Properties and Transport Air Quality (local & Americas) Ocean Fertilization (C cycle) Nutrient Supply (terrestrial productivity) [Highwood et al., 2003] Observed Saharan dust size distribution Simulated decrease in AOD Shifted mass to larger sub-micron sizes (less optically efficient). Reduces AOD in better agreement with satellite & AERONET observations

7. Dust Removal Across the Atlantic Model removal too strong, especially in winter-spring (transport towards Amazon). Likely excessive removal along the ITCZ. We estimate dust lifetimes in model (~3 days) in spring about 50% of satellite-based estimate (> 6 days). (Aerosol processing) Assuming first order loss can estimate lifetime from slope of log-plots… [Ridley et al., 2012]

8. Atmospheric Ammonia: A Source of Particulate Matter and Emissions on the Rise… AnimalsAgriculture NH 3 emissions major source of fixed N atmospheric acids (H 2 SO 4, HNO 3 ) Haber-Bosch Process (industrial production of NH 3 fertilizer) has dramatically increased global food production. …degrading air quality? now and in the future? Atmospheric NH 3 is sticky and semi- volatile with large dynamic range of concentrations: Difficult to measure. [Erisman et al., 2008] + =

9. Satellite Observations Providing Critical New Insights! New satellite measurements from IASI offer unprecedented monitoring of NH 3. Comparison with GEOS- Chem reveals springtime underestimate of emissions in the Midwest and year-round underestimate in the Central Valley of California. (Identify sources) [Heald et al., 2012]

10. The Importance and Challenge(s) of Organic Aerosol Globally OA makes up 25-75% of total fine aerosol at the surface. Could become more even more important in the future with sulfate clean-up? Models drastically underestimate. Source(s) unclear. [Heald et al., 2011] VOCs Range = 0.45-4.5 Primary Secondary oVOCs ? Average aerosol composition for 37 campaigns in the NH [Zhang et al., 2007] Model-measurement comparison for 17 aircraft campaigns

11. Using Satellite Observations to Constrain the Global Budget of Organic Aerosol [Heald et al., 2010b] Summer MISR AOD Simulated AOD from OTHER aerosol Residual = Organic Aerosol Satellite measurements indicate that total OA source is capped at 150 TgC/yr. This is still 3 times what is currently included in models. (Constrain budgets) TgC/yr

12. Is Organic Aerosol Contributing to Climate Trends in the SE US? Portmann et al. [2009] suggest cooling over the E. US (1950 to present) associated with biogenic aerosol. Goldstein et al. [2009] show large AOD enhancement over SE in summer. Strong seasonality seen in satellite AOD, but not surface PM 2.5. Explanation: aerosol aloft confirmed by CALIOP – inorganic or organic? SENEX 2013! (Reveal interesting disconnects, probe 3D distribution) [Ford and Heald, submitted] DJFJJA CALIOP GEOS-Chem

13. Conclusions Funding Acknowledgements: Satellite measurements fill much needed observational gap for aerosols But quantitative comparisons (moving beyond pretty pictures) can be challenging. 1.Interpretation of an integrated measurement (AOD), with complex retrieval algorithms. True uncertainties and biases not easily explored. 2.Retrieval algorithms not easily mimic’ed for models 3.Limited suite or sensitivity of aerosol precursor measurement from space (SO 2, NH 3, VOCs). 4.Daily snapshots (polar orbit) limit process quantification

14. First ever Official Atmospheric Chemistry Modeling Group Photo (2003) I might have been scared of Jennifer intimidated by inspired by