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Before/After Imagery

SA 2015 SA 2020

Figure caption: The slider above shows satellite estimates of NO2 from Aura’s Ozone Monitoring Instrument (OMI) as an average of April 15 through May 31 over South America. The image on the left shows the mean of the 230-day period from 2015 through 2019, while the image on the right shows the mean of the 46-day period for 2020. The sliders below show the same information, but zoomed to show five major South American cities. The images are free and publicly-available and may be downloaded.

Leyenda de la figura: el control deslizante de arriba muestra estimaciones satelitales de NO2 del Instrumento de Monitoreo de Ozono (OMI) de Aura, como un promedio del 15 de abril al 31 de mayo. La imagen de la izquierda muestra la media de un período de 230 días entre 2015 y 2019, y la imagen de la derecha muestra la media de un período de 46 días en 2020. Las imágenes son gratuitas, están disponibles públicamente y pueden descargarse en línea.

Legenda da Figura: O “controle deslizante” acima mostra estimativas de NO2 provenientes do Instrumento de Monitoramento de Ozônio (OMI) a bordo do satélite Aura, como uma média para o período de 15 de abril ate 31 de maio. A imagem à esquerda apresenta a média de 230 dias para o período entre os anos de 2015 até 2019, enquanto a imagem à direita mostra uma média de 46 dias para o mesmo período em 2020. Essas imagens estão disponíveis gratuitamente ao público e podem ser obtidas aqui.

buenos aires 2015 buenos aires 2020

The slider above shows satellite estimates of NO2 from Aura’s Ozone Monitoring Instrument (OMI) as an average of April 15 through May 31. The image on the left shows the mean of the 230-day period from 2015 through 2019, while the image on the right shows the mean of the 46-day period for 2020.

santiago 2015 santiago 2020

The slider above shows satellite estimates of NO2 from Aura’s Ozone Monitoring Instrument (OMI) as an average of April 15 through May 31. The image on the left shows the mean of the 230-day period from 2015 through 2019, while the image on the right shows the mean of the 46-day period for 2020.

rio 2015 rio 2020

The slider above shows satellite estimates of NO2 from Aura’s Ozone Monitoring Instrument (OMI) as an average of April 15 through May 31. The image on the left shows the mean of the 230-day period from 2015 through 2019, while the image on the right shows the mean of the 46-day period for 2020.

lima 2015 lima 2020

The slider above shows satellite estimates of NO2 from Aura’s Ozone Monitoring Instrument (OMI) as an average of April 15 through May 31. The image on the left shows the mean of the 230-day period from 2015 through 2019, while the image on the right shows the mean of the 46-day period for 2020.

2017-2019 SO2 in India 2020 SO2 in India
Image Credit: 

NASA GSFC

Figure caption: India recently became the world’s largest emitter of sulfur dioxide (SO2). The highest SO2 levels are over eastern India and primarily associated with electricity generation. Other sources in India include the ceramics industry. The slider above shows satellite data of SO2 from Aura’s Ozone Monitoring Instrument (OMI), averaging levels between March 25 and April 25. The image on the left shows the mean SO2 levels for 2017-2019, while the image on the right shows the mean for 2020. The decrease in SO2 levels in 2020 mostly reflect decreased power generation, likely attributed to the shuttering of businesses during India’s stay-at-home order. Independent estimates indicate that electricity generation for India was down about 10% and 25% in March and April 2020, respectively, as compared to March and April 2019. Another pollutant, NO2, is also emitted during thermal power generation and also showed a decrease in 2020 relative to previous years. One exception for SO2 is in southern India and it could be related to increased thermal power generation that came on line before the stay-at-home order. However, NO2 appears to not have had a similar increase over the area. More analysis is required to understand the cause. The images are free and publicly-available and may be downloaded.

LA 2015-19 LA 2020

Figure caption: On March 19, California was one of the first states to set mandatory stay-at-home restrictions in an attempt to slow the spread of COVID-19. Arizona and Nevada followed suit around April 1. The Ozone Monitoring Instrument (OMI) on board NASA’s Aura satellite provide data that indicate that these restrictions have led to about a 31% decrease in NO2 levels in the Los Angeles basin relative to previous years. NO2, or nitrogen dioxide, is an air pollutant measured by OMI. The estimated reductions for other cities in the Southwest U.S. before and after the quarantine restrictions are 22% for the San Francisco Bay Area, 25% for San Diego and Tijuana, Mexico, 16% for Phoenix, and 10% for Las Vegas. The slider above shows satellite estimates of OMI NO2 as an average of March 25 through April 25. The image on the left shows the mean of the 150-day period from 2015 through 2019, while the image on the right shows the mean of the 30-day period for 2020. The images are free and publicly-available and may be downloaded.

2005 EPA 2019 EPA
india map 2017 india map 2020

Figure caption: On March 24, 2020, Prime Minister Modi ordered a nationwide stay-at-home order for India’s 1.3 billion citizens in an attempt to slow the spread of COVID-19. As a consequence, less fossil fuels are being consumed and, subsequently, less air pollution is being emitted in India and also in neighboring countries, including Pakistan, Nepal, Bangladesh, and Sri Lanka. The slider above shows satellite data of NO2 from the Aura Ozone Monitoring Instrument (OMI) as an average of March 25 through April 25. The image on the left shows the mean of the period from 2017 through 2019, while the image on the right shows the mean for 2020. The slider shows that widespread decreases (~30-60%) in NO2 levels have occurred over most of South Asia. For instance NO2 levels decreased by about 45% in Lahore, Pakistan, 45% in Dhaka, and 55% in Delhi, India. The highest NO2 levels that remain in South Asia are located in eastern India and are primarily associated with electricity generation by thermal power plants. The images are free and publicly-available and may be downloaded.

Figure caption: Over the past several weeks, the Southeast U.S. has seen significant reductions in air pollution over many of its major metropolitan areas, such as Atlanta and Charlotte. Similar reductions in air pollution have been observed in the Northeast U.S., Florida, and across the globe. These recent improvements in air quality have come at a high cost, as communities grapple with the widespread stay-at-home advisories that began about a month ago as a result of the spread of COVID-19. Governor Roy Cooper issued a statewide shelter-in-place order for North Carolina on March 27. Other Southeast states followed suit within about a week. The slider above shows satellite data of NO2 from the Aura Ozone Monitoring Instrument (OMI) over the Southeast U.S. as an average of March 15 through April 15. The image on the left shows the mean of the period from 2015 through 2019, while the image on the right shows the mean for 2020. Though variations in weather from year to year cause variations in the monthly means for individual years, the data indicate that the NO2 levels in the last month are about 40% lower over the Southeast U.S. when compared to the mean of 2015 to 2019. In fact, March 15 – April 15 2020 shows the lowest value for the region as compared to any other year during the OMI data record, which spans 2005 to present. The NO2 levels are about 40% lower over Atlanta, Savannah, and Charlotte. Caution: Further analysis is required to rigorously quantify the amount of the change in NO2 levels associated with changes in pollutant emissions versus natural variations in weather. The images are free and publicly-available and may be downloaded. NEW! For technical experts: Global OMI NO2 Monitor.