Pollution SO 2 Studies: Air Quality and Satellites from the Local to Regional Scale Presented at UMBC June 7, 2007 Russell Dickerson Dept. Atmos. & Ocean Sci. The University of Maryland College Park Photo shot from UMD Research Aircraft Marufu, Doddridge, Taubman, et al.

Outline Air Quality issues for Maryland Satellite obs. vs. long-term averages & trends over N America. SO 2 and Aerosols over China. MODIS and CMAQ over the US. Future directions.

Research of Interest to Maryland Current ozone standard 85 ppb for 8 hr Baltimore and Washington should comply by 2009 LA, Houston, NY, NJ maybe not Proposed ozone standard ppb (2010) Many or most cities in North America will violate. Current PM2.5 (aerosol) standards 15  g m -3 annual average – Maryland is close (sulfate dominates) 35  g m -3 daily average – Maryland is close. Haze standard – return to pre-industrial levels by Must show progress.

Distribution and lifetime of SO 2.

Aztec-F Research Aircraft N500Z GPS Position (°Lat, °Long) Meteorology (T, RH, Pr, P alt, WS, WD) Carbon Monoxide (CO) Ozone (O 3 ) Sulfur Dioxide (SO 2 ) Aerosol Optical Properties: Absorption, b ap (565 nm) Scattering, b scat (450,550,700 nm) Aerosol Particle Size (MetOne) 6 cuts – Range µm

For measured SO 2 profiles with air from the Midwest.. 24 hour back trajectories

CMAQ and aircraft SO2 The average CMAQ SO 2 column content (14 mg m -2 ) is 1.5 times larger than the aircraft column content (9 mg m -2 ).

CMAQ and aircraft SO 2

GOCART and Aircraft GOCART average SO 2 column content (18 mg m -2 ) is 1.4 times larger than the aircraft column content (12 mg m -2 ).

GOCART and Aircraft

SO 2 lifetime The SO 2 profile shows a rapid decrease with altitude, nearing zero by 3000 m. If SO 2 is destroyed before it is advected away from the source, we can assume steady state conditions. Production of SO 2 = loss of SO 2 The loss over the area is the altitude integral of the product of concentration and the effective 1 st order rate constant, k`. Production (Flux) = Loss

Weighted flux from US states and Canadian municipalities (g hr -1 m -2 ). SO 2 column content (g m -2 ) Uncertainty = ( ).5 = 3 hours

Implications for S Chemistry. CMAQ and GOCART overestimate SO 2 in the PBL and especially LFT. Why? Emissions? No, they are the same. Loss rate too slow? Possible. The lifetime of SO 2 in the PBL in the summer over the NE US is only about 19 hr. Model has too little OH or H 2 O 2 ? Unlikely, H 2 O 2 is already in excess, and OH is ok. Deposition velocity too slow in model? Possible, would give the wrong profile. Cloud chemistry? Worth looking into further.

Fair Weather Cumulus

Two Reservoir Model (Taubman et al., JAS, 2004) Cu SO 2 H 2 SO 4

How are the satellites doing for long-term averages and trends in SO 2 and NO 2 ?

Average ( ) SO 2 burdens over USA, Aircraft summer mean 0.3 DU Thanks Nick!

Point Source Emissions 1999 Frost et al., JGR, 2006

SO 2 Trends NE China versus NE US (GOME and SCIA)

We focus on EAST-AIRE regional experiment over NE China in April SO 2 observations from instrumented aircraft flights are compared with OMI SO 2 maps. SO2 Aerosol Aircraft spirals

OMI Aerosol

EAST-AIRE Flights April 5, 2005 Heavy pollution ahead of cold front MODIS RGB imagery courtesy of the MODIS Rapid Response Project

The comparison demonstrates that operational OMI algorithm can distinguish between heavy pollution ( April 5 ahead of cold front ):

MODIS RGB imagery courtesy of the MODIS Rapid Response Project April 7: Shenyang area behind cold front

MODIS RGB imagery courtesy of the MODIS Rapid Response Project April 7: Shenyang area behind cold front

OMI directly measures integrated slant column absorption (SC+  ) along line of sight by fitting spectral lines Total SO 2 [molecules/cm 2 ]= (SC+  )/AMF Improving OMI SO 2 Retrieval Algorithm with Aircraft SO 2 Profile [N. Krotkov et al., NASA/GSFC]

And Aircraft Aerosol Information Operational AMF=0.36 Industrial aerosol (soot, small particles) OMTO3 measured slant column ozone: Dust aerosol (hematite, large particles) Aerosol properties were constrained in the visible wavelengths from aircraft integrated aerosol profile: AOT 500 ~1.1 SSA 500 ~0.9 [N. Krotkov et al., NASA/GSFC ]

Do Satellites See the Same Plume? EOS/Aura OMI EOS/Aqua MODIS OMI SO 2 MODIS AOD

Where Would the Plume Go on the Next Few Days? Forward Trajectories Initiated at Time of Satellite Observations on April 5. 04/05 05UTC 04/06 04UTC 04/07 03UTC

Can Satellites Track the Plume? Yes, On April 6, Roughly 65% of the Plume Captured by Satellites OMI SO 2 MODIS AOD

Can Satellites Track the Plume? Yes, But with Large Uncertainties On April 7, Roughly 30% of the Plume Captured by Satellites And More Interference of Clouds OMI SO 2 MODIS AOD

Change in AOD and Total SO 2 Loading in the Plume: Satellites Saw SO 2 -> Sulfate? Error bars yet to be added: but uncertainties likely to be large and may increase with time. SO 2 loss roughly corresponds to slightly less than 0.1 increase in AOD every day. But other factors, such as loss of primary aerosols and hygroscopic growth of aerosols, need to be taken into account.

SO 2 lifetime estimate By following the path of the air mass, and correcting for the altitude effect, the amount of SO 2 lost to dry deposition and chemical reactions was approximated. The mass decreases from the 5 th to the 7 th looks to be first order with a lifetime of ~4 d. The mass on April 8 shows no change from April 7 because the air mass was very disperse (large box) and mixed with other plumes.

OMI pollution SO 2 data quality The OMI measurements of SO 2 agree with the aircraft in situ observations of high concentrations of SO 2 (ca ~2 DU) ahead of the cold front and lower concentrations behind it. OMI (with a little help) can distinguish between background SO 2 conditions and heavy pollutions on a daily basis. Operational SO 2 data need correction for total ozone, SO 2 profile, viewing geometry and aerosol effects.

Congratulations Dr. Levy! Satellite vs. model aerosol optical depth. July 16, 2002 (typical pollution episode) CMAQ MODIS 0.0   1.0

Future directions: New Cascade Diode Laser NO 2 detector for aircraft. Refinement of SO 2 retrieval. Comparison of satellite, aircraft, & models (CMAQ; GOCART) over N America and E Asia. Influence of altitude, aerosols, background. Comparisons of MODIS aerosols to aircraft obs, lidar, and CMAQ. How do MM5, CMAQ, and WRF-CHEM do with clouds?

The End. Big thanks to Can Li, Nick Krotkov, Brittany McClure, Andreas Richter, and John Burrows.

←Top of afternoon PBL Carbon monoxide provides a good tracer for dynamics and test of emissions inventories.

Conclusions, continued:

(Regional Atmospheric Measurement Modeling & Prediction Program) (Regional Atmospheric Measurement Modeling & Prediction Program) Balanced Theory & Observations Observations Surface: Shenandoah National Park, VA Fort Meade, MD Philadelphia, PA Greenbelt, MD Piney Run, MD Aloft Aztec Aircraft Profiler Sondes Remote (NASA) TES/OMI etc. MOPITT (CO) TOMS (O 3 ) MODIS (particles) SCIAMACHY (SO 2, NO 2, H 2 CO … ) Input Emissions Inventories Emissions Models (Chem Engineering) MM5/WRF Dynamical Model 4-km Resolution Forecasting Chem/Trans Models CMAQ Modular Open Code Collaborative w/EPA or GOCART Global Photochem. Aerosols Transport Deposition

General Study Area & Spiral Locations Summer observations over eastern North America General subsidence (Bermuda High) Cloud pumping through fair weather cumulus. Aircraft and satellite observations.

Aerosol Scattering

Conclusions CMAQ under-predicts O 3 aloft by 10% (~6 ppb). CMAQ does not account for aerosols when calculating reaction rates for photolysis of NO 2. –By accounting for typical aerosols measured, and using photolysis rates associated with those aerosol measurements, O3 increases by 1-2% (~1 ppb). CMAQ and GOCART over-predict SO 2 by 20 – 40% near the surface  The assumed lifetime is too long. –Possible reasons for the over-prediction include errors in emissions and/or errors in cloud cover – leading to less reactions of SO 2 and H 2 O 2 in clouds. The average SO 2 lifetime calculated using 180 measured profiles (from the summer in the Mid-Atlantic region) and EPA and Environment Canada emissions was 18 +/- 6 hrs (95% C.I.).

CMAQ under-predicts O 3 by 10% (6 ppb) between 600 and 2600 m.

Average ( ) SO 2 burdens over USA, Europe and China: 25.5 million tons of SO 2 were emitted by Chinese factories in 2005 up 27% from 2000 East-Aire’05 experiment Aircraft summer mean 0.3 DU

50 GOME & SCIA NO 2 : US Power Plant NOx reductions After 2000, clear decrease (> 30%) in NO 2 in Ohio River Valley area. (SIP-Call) Little change over East Coast