Air Quality from Space Bryan N. Duncan Atmospheric Chemistry and Dynamics Laboratory NASA Goddard Space Flight Center Photo from NASA Skylab in 1973 of Los Angeles smog. Satellites provide a “birds eye” view.

Air Quality Smog = a noxious mixture of particulates & gases Beyond trends – processes that control ozone In the US, 120 million people currently live in areas that do not meet air quality standards

Where there are lights, there is pollution! Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite

Answer: Spatial coverage. Question: Why does NASA monitor pollution? Isn’t that the job of the EPA? Answer: Spatial coverage. Instruments on NASA satellites can measure pollution over the whole U.S. and even the whole globe. Surface measurements are sparse and don’t give us the whole air pollution picture.

Haze over the Mid-Atlantic Pollution has a global impact via long-range transport! True Color Image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite

What are NASA instruments measuring?

Ozone ●The ozone standard is currently 75 ppbv as averaged over 8-hours. ● A new rule may lower the standard to 60 ppbv = European standard. Source of graphic: Wall Street Journal, July 21, 2011

A Quick Tutorial…. “Good” Ozone “Bad” Ozone Blocks most UV rays Damages Lungs

Formaldehyde – a proxy for VOCs – a precursor to ozone Isoprene is a VOC emitted from trees & emissions increase with temperature. HCHO is a product of isoprene oxidation, so variation in the concentration of HCHO can serve as a proxy for variation of isoprene. Isoprene plays an important role in the formation of unhealthy levels of ozone – more important than anthropogenic VOCs, so must decrease NOx to decrease ozone! Ozone Monitoring Instrument (OMI) on the Aura satellite

Nitrogen dioxide is another precursor to ozone Google Earth image of NO2 over Texas, July 2006. Note the locality of population centers with respect to high NO2 concentrations Ozone Monitoring Instrument (OMI) on the Aura satellite NO2 is an EPA criteria pollutant as well.

Regulations of NOx Emissions are Working! NO2 decreases by 20-50% 2010 2005 Ozone Monitoring Instrument (OMI) on the Aura satellite

2005-2007 2008-2010 SO2 Reductions over the Eastern US as Seen by OMI When combusted, coal with sulfur impurities leads to the formation of SO2 – a precursor to acid rain and PM2.5. 2005-2007 2008-2010 Ozone Monitoring Instrument (OMI) on the Aura satellite

And for perspective … OMI SO2 China 2005 mean OMI SO2 US Ohio Valley 0.0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 SO2 Column (DU) OMI measurements show that SO2 was very high in China (2005) and much lower over the Ohio valley in the US. The SO2 in China comes from power plants without scrubbers burning high sulfur coal. The 1971 Clean Air Act mandated scrubbers on US power plants built after 1977.

Sulfur Dioxide 2005-2007: increasing power plant emissions 2005 2006 Chinese SO2 emission controls were strengthened by the 11th Five-Year- Plan that requires flue-gas desulfurization technology (FGD) on all new plants and some old ones. There is also better inspection and enforcement. The maps show July monthly average column amounts of sulfur dioxide (SO2) from the Chinese coal burning power plants, smelters and still mills measured by the Ozone Monitoring Instrument on NASA’s Aura satellite. The measurements are for the years of 2005- 2009 (left to right). The images show monthly averaged SO2 data, excluding cloud cover. Sulfur dioxide in these images is measured in Dobson Units (DU). If you compressed all the sulfur dioxide in a column of the atmosphere into a flat layer at 0 degrees Celsius (32 degrees Fahrenheit), at the pressure at the Earth’s surface, a single Dobson Unit of SO2 would measure 0.01 millimeters in thickness and would contain 0.0285 grams of sulfur dioxide per square meter. The Dobson Units range from less than 0.5 (pale lavender-pink) to 3.0 (red). Red color indicates highest persistent pollution downwind of regions with industrial activity. OMI SO2 data show a noticeable increases between 2005 and 2007, but decrease in the 2008-2009 SO2 burdens compared to the previous years. These are DIFFERENT COLOR SCALES FROM PREVIOUS PAGE (MAX 0.5 DU on that page, here it’s 2) Relevance for future science and relationship to Decadal Survey: Aura OMI will continue monitoring Chinese SO2 pollution from space to detect future pollution reductions. It’s imperative to maintain and continue our SO2 observational record to show that Chinese emission controls are working. 3) Ozone Monitoring and Profiling Suite (OMPS) instrument is slated for the NPP mission. OMPS will continue the total ozone and SO2 observational record. 2) Globally using OMI data we can directly compare SO2 pollution level in different regions of the world. 4) Decadal Survey recommended the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission that will allow more frequent monitoring of SO2 pollution over N and S America. NASA Aura Ozone Monitoring Instrument boundary layer SO2 dataset: Data Source: http://disc.sci.gsfc.nasa.gov/Aura/data-holdings/OMI/index.shtml/omso2g_v003.shtml 2008 2008: Beijing Olympics, stringent emission control measures were enforced 2009 2009: Global economic crisis, reduce industrial activity and strict emission controls continue 14

The Impact of the 2005 Gulf Hurricanes on NO2 Difference in OMI NO2 (Pre Katrina - Post Rita *) Destroyed Oil Platforms (, ) Katrina Refineries New Orleans LA Offshore Oil Port reopened Nov. 5th Rita Landfall Sep. 24th Aug. 29th x1015 molec/cm2 Reductions in Oil & Gas Production * Pre Katrina = August 1 - 26 Post Rita = September 27 - October 17 Katrina Rita Wilma Production [%] Hurricanes Katrina and Rita caused a significant reduction in NO2 emissions from oil and gas production facilities as well as power plants. Date

Wildfires & Agricultural Fires Cold Front Agricultural Fires But how does satellite AOD (unitless) relate to “nose-level” PM2.5 (ug/m3)? AOD = Aerosol Optical Depth the degree to which aerosols prevent the transmission of light by absorption or scattering of light through the entire vertical column of the atmosphere from the ground to the satellite’s sensor.

PM2.5 Estimation: Popular Methods Difficulty Level Two Variable Method Multi-Variable Method Artificial Neural Network MSC   AOT PM2.5 Y=mX + c

Satellite-Derived PM2.5 [ug/m3] This is widely used method. I believe UNEP has adapted these data sets in their report. This is from Randal Martin’s group.