The Science Behind Satellite-Based Air Quality Monitoring

The Science Behind Satellite-Based Air Quality Monitoring

The Science Behind Satellite-Based Air Quality Monitoring

By Ben Moose, Gasp Spring Intern

In my last blog post, I provided an overview of the concept, methods, advantages, and disadvantages of remote atmospheric monitoring. In this post, I will describe, in more detail, the techniques satellites use to detect air quality – how instruments can measure the concentration of gases and pollutants remotely. I will focus specifically on the TROPOMI device to illustrate the capabilities and recent advancements in the field, as it is one of the newest and most effective devices for air quality measurements.

How does TROPOMI measure pollutants?

As noted in my last post, TROPOMI allows beams of light reflected off of the atmosphere to enter the device. Instruments in the device then determine the wavelength of the measured light using wavelength detectors. As different gases in the atmosphere absorb light at different wavelengths, TROPOMI can determine the concentration of different gases in the atmosphere by comparing the wavelengths of reflected light to sunlight. For example, ozone absorbs light energy at wavelengths of approximately 500 – 700 nanometers. TROPOMI compares a sample of light directly from the sun to a sample of light reflected through the atmosphere, and the difference in light energy at wavelengths of 500 – 700 nanometers illustrates the concentration of ozone in the atmosphere. This process is called spectrometry, and the instrument used in TROPOMI is a multispectral imaging spectrometer, as it can detect a variety of wavelengths of light across different spectrums.

Why is TROPOMI so useful compared to other satellites?

Range of measurement: TROPOMI, unlike other satellites used to detect air quality, can measure wavelengths in multiple different spectrums. Specifically, the device can detect wavelengths in the ultraviolet, visible, near-infrared, and short-wave infrared spectrums. TROPOMI’s access to a variety of different wavelengths allows it to simultaneously detect multiple gases that absorb different wavelengths of light, allowing the device to measure a wide range of pollutants and indicators of air quality that other devices cannot measure. The image on the right illustrates TROPOMI’s measurement capabilities.

The bands of wavelengths at which different gases or pollutants absorb light energy are visualized with white bands on the chart, and the measurement abilities of different satellites are included at the top and bottom of the image. As shown in the chart, TROPOMI can detect substances in the atmosphere that absorb light at wavelengths of approximately 250-500 nm, 700-800 nm, and in a narrow band above 2000 nm.

Accuracy and resolution:  As the above visualization of the satellite ranges illustrates, other devices such as SCIAMACHY and GOME have very large ranges of wavelength detection, allowing these satellites to measure more indicators than TROPOMI. However, the main factor setting these devices apart is the resolution. While TROPOMI can measure pollutants and gases at a 7.0 km x 3 km resolution for most scans, SCIAMACHY’s resolution, for example, is about 200 km x 30 km. This huge difference in resolution allows the newer TROPOMI device to more accurately measure air quality with local measurements, despite its lack of ability to measure some air quality indicators. The visualization below illustrates the  resolution of the four satellites included in the above chart, centered around the Amsterdam area.

 

Useful additional resources

This World Meteorological Organization site provides information about the different measurement capabilities of the TROPOMI device, as well as other satellite devices. It includes a list of different air quality and atmospheric indicators (gases, pollutants) and the satellite’s  effectiveness at measuring each one, along with the measurement method. 

This page of the Delft University of Technology’s website outlines the benefits of TROPOMI when compared to other satellites, and is the source of the images used in this post.

 

An Overview of Remote Atmospheric Monitoring

An Overview of Remote Atmospheric Monitoring

An Overview of Remote Atmospheric Monitoring

Data from the TROPOMI device illustrating the patterns of sulfur dioxide spread in Norilsk, Russia. Topography and wind speed as illustrated in the data overlay, have significant impacts of the spread of polluted air. Source: Jonathan Amos, BBC.

By Ben Moose, Gasp Intern

What is remote atmospheric monitoring?

Remote atmospheric monitoring, when used for air quality monitoring purposes, is the use of satellites and satellite instruments to determine the concentration of pollutants and other air quality indicators present in the atmosphere. One leading organization in the field of satellite air quality detection is the Copernicus Atmosphere Monitoring Service (CAMS). CAMS uses atmospheric computer-based models, along with satellite data and surface-based sensor data, to develop maps and measurements of global air quality. In order to collect satellite data, CAMS uses TROPOMI (Tropospheric Monitoring Instrument), a device on the Sentinel – 5P satellite which collects information about multiple air quality indicators and their atmospheric concentrations at an unprecedented resolution.

 

What are the advantages and disadvantages of remote air quality monitoring when compared to direct detection?

Accuracy – Although not as locally accurate as a surface-level air monitoring device such as those installed by the EPA around the country, TROPOMI can measure some air quality indicators such as sulfur dioxide at a 3.5km x 7km resolution, allowing for not just national, but regional and local air quality to be measured. This level of accuracy enables the detection of specific areas in which air quality issues need to be addressed. For example, TROPOMI data from Norilsk, Russia is shown in this image, illustrating the capability of the Sentinel – 5P satellite in terms of local air quality observation.

Cost – Although expensive to develop the equipment on the Sentinel – 5P satellite, TROPOMI allows for global atmospheric monitoring. On the other hand, EPA – installed local monitors can cost upwards of $10,000 just for sensors detecting one indicator, and can only gather data from a fixed location. Because of this cost difference, remote monitoring is the most efficient and practical method of gathering air quality data for most of the country and world, with a likely exception being urban areas with highly variable air quality based on specific location, time, or season.

Reliability – Many surface-based air quality monitoring sites do not regularly measure some air quality indicators. For example, the EPA network of sensors includes multiple devices in the Birmingham metropolitan area, but the most recent data points for many indicators such as sulfur dioxide are months in the past, so current air quality data is difficult to obtain. On the other hand, the Sentinel – 5P satellite, for example, is capable of measuring air quality data once every 24 hours for a given location, providing more recent data which is likely more accurate and useful for residents and organizations.

What services can use data from remote atmospheric monitoring systems?

The data gathered by TROPOMI and analyzed by CAMS is used to allow weather applications and services (such as the Weather Channel app) to provide local air quality information, either through combination with existing surface measurements or using satellite data alone. Remote atmospheric monitoring allows these applications to display up-to-date information on a variety of different air quality indicators that affect air quality indices, such as sulfur dioxide, ozone, and nitrogen dioxide.

Helpful resources

  • Charts showing current air quality overlayed onto a visualization of the Earth. The data in these charts is obtained from the Sentinel-5P satellite and TROPOMI device.
  • A page of TROPOMI’s website that gives an overview of the different indicators measured by the device, as well as links to data from the satellite and a more in-depth description of the measurement of each indicator.
  • A BBC article describing the use of the Sentinel – 5P satellite to gather air quality data including an estimation of production of sulfur dioxide in Norilsk, Russia. The article provides examples of visualizations using TROPOMI data.
  • A map of EPA air quality monitors with data about functionality and measurements, as well as the different types of indicators that each sensor measures.
  • A World Meteorological Organization webpage that describes the methods in which the TROPOMI device measures different indicators of air quality, as well as the limitations of these measurements.
  • A PDF file of the TROPOMI brochure with information about its measurement methods, construction, and functions.

 

Sources

http://www.aqmd.gov/aq-spec/home

https://www.spaceoffice.nl/files/documenten/16.0808%20Tropomi%20brochure%20ENG%203.pdf

https://www.wmo-sat.info/oscar/instruments/view/586

https://www.spaceoffice.nl/nl/activiteiten/nationaal-programma/nationale-projecten/tropomi/

https://epa.maps.arcgis.com/apps/webappviewer/index.html?id=5f239fd3e72f424f98ef3d5def547eb5&extent=-146.2334,13.1913,-46.3896,56.5319

https://www.bbc.com/news/science-environment-44705268

http://www.tropomi.eu/data-products/level-2-productsNorilsik

https://atmosphere.copernicus.eu/charts/cams

Header Image: PhysicsWorld, Photo credit: ESA/ATG medialab. 

Meet Brodie Zalanka, Spring Gasp Intern

Meet Brodie Zalanka, Spring Gasp Intern

Meet Brodie Zalanka, Spring Gasp Intern

​What is your major at UAB/BSC and why did you choose it? I have a Bachelor of Science in Public Health and am pursuing my Masters in Public Health with a concentration in environmental and occupational health.

What do you hope to do after you graduate? I am considering continuing my education and pursuing my Doctorate degree in philosophy of environmental health sciences. 

What is your dream job? I want to eventually work in a leadership position at the EPA.

What do you hope to learn while interning with Gasp? I want to learn more about air quality and the methods of reporting pollution.

Why is our mission to reduce air pollution important to you? As a former Army medic, I have been trained to support and advocate for the preventative side of health issues. I see a direct correlation of environmental influences impacting health. I wish to be a part of the system that aims to decrease pollutants that negatively impact everyone’s life.

What is your favorite food? Cheeseburgers!!!

What are your hobbies? I love camping and fishing.

Who or what are your influences? My family is a tremendous influence for me. I am also influenced by more former Battalion Command team and platoon Sergeant. 

What are some other fun facts about yourself?

  • I love to BBQ.
  • Have an awesome girlfriend.
  • Have a dog and cat.
  • I am a retiree.

Meet Mimi Tran, Spring Intern for Gasp

Meet Mimi Tran, Spring Intern for Gasp

Meet Mimi Tran, Spring Intern for Gasp

​What is your major at UAB/BSC and why did you choose it? I’m a freshman Urban Environmental Studies major at Birmingham Southern College. As a kid, my favorite part of family vacations was (and still is!) visiting a city’s botanical gardens, local farmers markets, or urban parks. I am fascinated about ways of daily sustainable living from tiny houses to Earthships and eco-friendly city structures. Constructed as an interdisciplinary major, Urban Environmental Studies allows me to bridge the relationships between society and our natural environment.

What do you hope to do after you graduate? After graduation, I hope to pursue a career in public service. Whether that be through the government or nonprofit sector, I am most called towards advocacy work. Currently, I work with various civic organizations on social justices causes, aiming for a more inclusive and connected community. In the future, I hope to work more directly with Alabama’s state policies, particularly on environmental justice, women’s health care, and sex education. 

What is your dream job? While there are many careers I’d love to experience一like being a part of a botanical garden design team!一ultimately, I want to serve in public office, concentrating on community development, particularly through inclusion and green initiatives.

What do you hope to learn while interning with Gasp? While interning at GASP, I hope to grow closer to and more involved with the larger Birmingham community. In addition, I’m excited to learn more about community environmental initiatives, especially what social, political, and environmental methods we can apply to the environmental injustice prevalent in northern Birmingham communities. 

Why is our mission to reduce air pollution important to you? Birmingham’s air pollution is intertwined with political, social, and racial issues. A person’s access to life’s necessities such as the ability to breathe clean air is not a privilege for the powerful or wealthy, but a human right. As an Alabama native, a young woman and an Asian American, I understand the necessity to fight for a community that is conscious and inclusive of minority and marginalized groups. Through GASP’s mission, I believe we are not only working towards a healthy community, but a unified city. 

What is your favorite food? I eat anything and everything! But I’m always in the mood to eat curry! From different Indian curries to Thai, they always remind me of home. 

What are your hobbies? While I do consider my love of food adventures a hobby, I also love journaling, playing instruments, reading, and doing anything outdoors. From hiking to kayaking, I feel most at peace when I’m outside! 

Who or what are your influences? I grew up with a big family and since I was a kid, they have been my biggest supporters and sturdiest foundation. My parents who both immigrated to America for better life opportunities have endlessly encouraged me to pursue my passions and ambitions. 

What are some other fun facts about yourself?I play three instruments一piano, guitar, and ukulele! I love musical theatre! Some of my favorites include Waitress and Les Miserables.

 

Meet Matthew Odendahl, Spring Intern for Gasp

Meet Matthew Odendahl, Spring Intern for Gasp

Meet Matthew Odendahl, Spring Intern for Gasp


Matthew is serving as Gasp’s Communications and Marketing Spring Intern

What is your major at UAB/BSC and why did you choose it? I am pursuing a bachelor of science in public health, with a concentration in environmental health and a studio art minor.  I chose this degree as I wanted to have a positive impact on the world and as I kept studying and taking classes I realized that I had skills that could be beneficial for addressing community concerns and the environment.

What do you hope to do after you graduate? I hope to work with local organizations to help make Birmingham the city that I believe it could be.  

What is your dream job? My dream job would have to be a position where I am allowed to be creative while also being able to listen and help vulnerable communities. 

What do you hope to learn while interning with Gasp? I hope to learn how to not only help vulnerable communities and populations but also have a lasting positive impact on them as well.

Why is our mission to reduce air pollution important to you? Poor air quality affects everyone but really has an impact on communities located by industry.  People living in those areas have higher rates of asthma, lung cancer, etc and are economically trapped there due to systems of oppression.  This vicious cycle makes me feel ashamed of my home so I want to fix those issues.  

What is your favorite food? I would have to say my favorite food is some sort of sandwich, turkey, meatball doesn’t matter.  I enjoy efficient foods and what’s more efficient then a sandwich? It has everything you need in each bite.  Perfection. 

What are your hobbies? I am an artist so I spend a lot of my free time illustrating, painting, anything where I can create and explore my mind.

Who or what are your influences? I have many influences in my life.  I am moved by artists both music and visual who use their experience to create.  I am inspired by my mentors and professors that have instilled in me information that can be utilized to make the world better.  I am inspired by my peers that take action and stand up for what they believe in.  

What are some other fun facts about yourself?

  • I listen to rap music religiously. 
  • I hate driving so I tend to walk most places. 
  • I love art and expression in all its forms
  • I consider most foods encased in something a sandwich ie burrito, gyro, hotdog etc.