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

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air quality from space

Air Quality from Space

Photo from NASA Skylab in 1973 of Los Angeles smog.

Satellites provide a “birds eye” view.

Bryan N. Duncan

Atmospheric Chemistry and Dynamics Laboratory

NASA Goddard Space Flight Center

air quality
Air Quality

Smog = a noxious mixture of particulates & gases

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


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



●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

Blocks most UV rays

“Bad” Ozone

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 d ioxide is another precursor to ozone
Nitrogen dioxide is another precursor to ozone

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%



Ozone Monitoring Instrument (OMI) on the Aura satellite


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.



Ozone Monitoring Instrument (OMI) on the Aura satellite

and for perspective
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




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.


2008: Beijing Olympics, stringent emission control measures were enforced


2009: Global economic crisis, reduce industrial activity and strict emission controls continue




Aug. 29th

New Orleans


LA Offshore Oil Port reopened Nov. 5th



Sep. 24th

The Impact of the 2005 Gulf Hurricanes on NO2

Destroyed Oil Platforms (, )

Difference in OMI NO2

(Pre Katrina - Post Rita *)


Reductions in Oil & Gas Production

* Pre Katrina = August 1 - 26

Post Rita = September 27 - October 17




Production [%]

Hurricanes Katrina and Rita caused a significant reduction in NO2 emissions from oil and gas production facilities as well as power plants.



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.

pm 2 5 estimation popular methods
PM2.5 Estimation: Popular Methods

Difficulty Level

Y=mX + c