The Steaks are High! Methane on the Rise

Category: Assessing Air Quality and Water Resources
Project Team: San Francisco Bay Area Health & Air Quality
Team Location: NASA Ames Research Center – Moffett Field, California

AJAX flight path over the San Francisco Bay Area with points indicating methane concentrations from low (green) to very high (red). Image Credit: San Francisco Bay Area Health & Air Quality team

AJAX flight path over the San Francisco Bay Area with points indicating methane concentrations from low (green) to very high (red). Image Credit: San Francisco Bay Area Health & Air Quality team

Maya Midzik
Joseph Abbate
Garima Raheja

Dr. Abhinav Guha (Bay Area Air Quality Management District)
Dr. Laura Iraci (Ames Research Center)
Dr. Josette Marrero (NASA Postdoctoral Program)
Warren Gore (Ames Research Center)
Dr. Emma Yates (Bay Area Environmental Research Institute)
Dr. Juan Torres-Pérez (Bay Area Environmental Research Institute)

Past/Other Contributors:
Chippie Kislik (Center Lead)


Methane, or CH4, is the second-most important anthropogenic greenhouse gas in terms of radiative forcing, with emissions coming from a variety of human-induced sources in populated areas, such as livestock, landfill, and wastewater. The Bay Area Air Quality Management District (BAAQMD) uses traditional bottom-up methodologies to produce source-specific emissions estimates for their regional greenhouse gas inventory; however, recent literature demonstrates that bottom-up methodologies are underestimating CH4 emissions by up to 50 percent in many regions of California, including the San Francisco Bay Area. This discrepancy is investigated in this project by comparing ground-based in situ greenhouse gas measurements with sub-Planetary Boundary Layer aircraft measurements from the NASA Alpha Jet Atmospheric eXperiment (AJAX). Understanding the spatial and temporal variations in CH4 can help identify hotspots and trace the sources of high-CH4 plumes. Integrating these findings into their traditional bottom-up methodologies has offered a more accurate approach to compiling this inventory. Furthermore, the identification of possible high-emission point sources may suggest areas of future in situ measurement for the agency’s Mobile Greenhouse Gas Measurement Network, or remotely sensed total column measurements by targeted greenhouse gas satellites such as Greenhouse Gases Observing Satellite (GOSAT).

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Daryl Ann Winstead (Mekong River Basin Agriculture) 18-08-2016, 16:01

Great project and interesting video! Did the AJAX data have to be processed before using it? If so, what do the processing steps consist of? Thanks in advance for your response!

Garima Raheja 18-09-2016, 14:16

Hi Darryl– thanks for the question. Yes, the AJAX data had to be processed before we could use it. We had to detect the height of the planetary boundary layer for each flight– we wrote an algorithm to use meteorological measurements to do this. The AJAX team also smooths out the data in 3s intervals to remove instrument noise.

Nirav Nikunj Patel 18-08-2016, 10:19

Fantastic Project and Visuals! Out of curiosity, what is the spatial resolution of the data collected on the AJAX flights? Very important work here to make the bottom-up methodologies more accurate!

Garima Raheja 18-09-2016, 14:18

Hi Nirav– thanks for the comment. The AJAX data is collected at 3 Hz, so the spatial resolution will depend on how fast the plane is flying at any given time. You can get a sense of the spatial resolution from the image above called “AJAX flight path over the San Francisco Bay Area with points indicating methane “AJAX flight path over the San Francisco Bay Area with points indicating methane.” I hope this helps!

Sara H Lubkin 12-08-2016, 17:30

Awesome video! And a very cool project. What were the biggest challenges?

Maya Midzik 18-08-2016, 02:32

Hi Sara- thanks for your question! I would say the biggest challenge in our research was figuring out how to define the planetary boundary layer for each flight and be sure that we were getting valid low-altitude data. We wanted to be sure that we including only local methane, rather than long-lived methane from distant sources.

Molly Spater 12-08-2016, 11:35

What a fantastic video! I really appreciate the time you all took to use watercolor and really make your VPS dynamic. I also am very interested in ways in which satellite data can be combined with aerial data. I think your team did a great job explaining that and the rest of your project in your VPS.

Maya Midzik 18-08-2016, 02:43

Hi Molly- thanks for your feedback and question. In terms of greenhouse gas (GHG) monitoring, it’s difficult to combine satellite and airborne data on such a local scale. Most greenhouse gas monitoring satellites (TES, AIRS and SCIAMACHY, for example) monitor GHGs in the lower stratosphere/upper troposphere- so they never even reach the lower altitudes we were interested in for local pollution. The Japanese satellite GOSAT is able to take full-column measurements (down to the lower troposphere), however GOSAT doesn’t take continuous measurements and has targeted California infrequently. In summary, satellites and aerial data can’t be combined at the moment to comprehensively measure greenhouse gasses over the SF Bay area. We also looked into a number of ways that visual satellite and aerial data could be used to supplement/validate the BAAQMD spatial emissions inventory, including the use of high resolution satellite imagery and USGS high-resolution orthographic imagery to identify the locations of dairies, landfills, and other emissions sources. We didn’t have time to fully implement these ideas during this term, but hopefully a future term of the project will.


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