Background ozone and implications for air quality management

In a new paper published in Elementa, Dan Jaffe and his coauthors look at background ozone in the US and how it influences whether states can meet air quality standards. Background ozone (O3) includes “contributions from natural and foreign sources of O3 that cannot be controlled by precursor emissions reductions solely within the US.” Understanding background O3 is necessary for air quality management overall and for states and municipalities to meet national air quality standards.

They examined over 100 published studies in order to assess what is the current knowledge about the distribution, trends, and sources of background ozone in the continental US. They found that “noncontrollable O3 sources, such as stratospheric intrusions or precursors from wildfires, can make significant contributions to O3 on some days, but it is challenging to quantify accurately these contributions.” In order to address this shortcoming, they recommend a more coordinated and focused approach to understanding background ozone in the US: improvements in the monitoring network, large-scale field experiments, more accurate and consistent chemical transport models, and more detailed observations of wildfires.

Read the paper here

Court decision on Oakland coal terminal

An article in the East Bay Express discusses the court decision on the coal export terminal that developers propose to build near the foot of the Bay Bridge in Oakland. Earlier this year, a U.S. District Court judge overturned Oakland’s ban on storing and handling coal at this planned marine terminal. Judge Chhabria found that there wasn’t enough evidence to support Oakland City Council’s assertion that “the proposed coal operations would pose a substantial danger to people in Oakland.” ESA, an environmental consulting firm, helped the city study the possible environmental impacts of shipping coal by train to the terminal. They found the scientific research on coal dust emissions from trains extremely lacking. In fact, they could find only one recent, peer-reviewed scientific study focusing on coal dust emissions from trains: the 2014 Jaffe Group paper “Diesel particulate matter and coal dust from trains in the Columbia River Gorge, Washington State, USA.”  Judge Chhabria agreed with the city that some level of coal dust pollution is likely but said that the city couldn’t show exactly how much and what the health and safety impacts would be. Scientific research on the effects of coal dust emissions on public health in urban areas is limited. Oakland is currently appealing the court’s decision.

Read the East Bay Express news article here

Postdoctoral Research Associate openings

The Jaffe Research Group has openings for 1–2 postdoctoral fellows who will focus on understanding gas and aerosol chemistry from global and regional sources.

  • One position will focus on collecting and interpreting observations from the Mt. Bachelor Observatory (MBO), an NSF-funded observatory that we have operated since 2004. MBO measures a suite of key gases and aerosol components (e.g.,O3, CO, CO2, σscat, σabs) year round. During spring and summer intensives, additional measurements (NOx, NOy, VOCs, aerosol chemistry, and physics) are added to focus on specific research questions.
  • The second position will study O3, NOx, and VOC chemistry in wildfire plumes as part of the NOAA FIREX campaign.

The primary responsibilities for these positions include:

  • Making high quality observations of atmospheric constituents.
  • Interpretation of the data with other observations, such as meteorology, regional air quality, satellite data, and air quality models.
  • Publishing the results in top scientific journals.

Qualifications include:

  • PhD in Chemistry, Atmospheric Sciences, Geosciences, or a closely related field.
  • Strong expertise in one or more of the following areas: instrumentation for gas and aerosol measurements (especially VOCs by GCMS), data interpretation, integration of satellite data, and modeling of transport and chemistry.
  • Good communication skills and experience publishing in scientific journals.

Appointments will be for one year with possible extensions. Compensation is competitive and post docs receive a full benefits package.

To apply and to see the full position description, see For more information, contact Dan Jaffe at

The positions are available immediately and will remain open until filled.

US particulate matter air quality improves except in wildfire-prone areas—See our new group paper!

A new paper authored by Crystal McClure and Dan Jaffe describes the increasing  particulate matter (PM2.5) pollution over the last few decades in the Northwest. This research, published Monday in Proceedings of the National Academy of Sciences, analyzed PM2.5 data from rural monitoring (IMPROVE) sites across the contiguous US for 1988–2016. They found a decreasing trend  in PM2.5, and cleaner air, around the country except for in the Northwest, where there is a positive trend in PM2.5. This positive trend is associated with total carbon, a marker for wildfires.

The figure below shows trends in PM2.5 for 1988–2016 for the 98th quantile, that is, the seven highest days. In most of the Northwest (red and orange areas), these days are getting worse, while most of the country has improving air quality trends (purple, blue, and green areas).

Figure 1 in PNAS paper US particulate matter air quality improves except in wildfire-prone areas

The 98th Quantile Regression of PM2.5 trends. Observed PM trends for 1988–2016 (calculated using QR methods) from IMPROVE sites are shown by black dots with corresponding values in µg·m−3·y−1. Krige-interpolated values (calculated from observed data) are shown by the color ramp. Solid black lines with arrows (indicating direction) show the boundary where the Krige-interpolated PM2.5 trends within have a 90% probability of being positive or negative. Of the 157 sites, 92 show statistical significance (8 positive/84 negative).

Read the abstract on the PNAS website

This new research has been garnering a lot of press since its publication:

Purple reigns for new PhDs

Let me introduce you to our newest graduates, Dr. Crystal McClure and Dr. Pao Baylon! A few raindrops didn’t diminish their sunny smiles and the cheering crowd as they marched at the University of Washington’s graduation on June 9, 2018. We celebrate your success and are so excited for both of you!

Pao is employed at the Idaho Department of Environmental Quality in Boise. Crystal will begin a post-doctoral fellowship at UC Davis in August.