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Aura Science

Nitrogen Dioxide Data to Show A Relationship Between Air Quality Changes & Economic Growth Globally

Satellites offer an unprecedented opportunity to evaluate patterns and trends in air pollution, especially in regions with few or no ground-based monitors.

We evaluate the 100 most populous cities worldwide, comparing the OMI nitrogen dioxide (NO2) vertical column densities from the Aura satellite to population, gross urban product (GUP), and emissions estimates. We find a positive relationship between GUP and NO2 for 38 of the 56 low-income cities, where NO2 increases with GUP, and a negative relationship for the 7 high-income cities, where NO2 decreases with GUP.

This trend is consistent with the environmental Kuznets curve model. However, we found the GUP of 36 cities in the middle range of incomes did not display any consistent relationship with NO2. This partial Kuznets curve relationship arises across the 2005 to 2011 years of our study period, where specific cities show a positive or negative trend in NO2 with GUP growth over time. We analyze a global emissions inventory to compare the relationship between GUP per capita and pollution, which shows a similar relationship. The difference between observed NO2 and the emissions inventory could be due to atmospheric processes or could be due to city-specific changes in energy that are not well captured in the inventory.

NOx is well suited as a metric for the relationship between economic growth & air quality (AQ) since direct health impacts of NOx exposure have been identified & NOx is an important precursor to particulate matter (PM) formation & near-surface ozone.

Using Aura OMI NO2 vertical column densities (VCDs) as an indicator for NOx, relationships between Growth Urban Product (GUP; i.e., economic development) & AQ are investigated globally with differences discovered between low & high income cities.

Lower-income cities: Increasing OMI NO2 with increasing GUP from industrialization & increasing energy consumption.

Higher income cities: Typically decreasing NO2 with increasing GUP due to emission controls & pollution regulations adopted.

Comparison of change in GUP per capita with change in NOx from 2005 to 2011 for the 100 largest global cities

Comparison of change in GUP per capita with change in NOx from 2005 to 2011 for the 100 largest global cities, grouped by the World Bank Organization’s (WBO) Region of Economic Development with NOx indicated by NO2 VCD from the OMI instrument.
The map indicates the region on the scatter plot by color.

Scientific significance, societal relevance, and relationships to future missions:

This study examines the relationship between economic growth and air quality (NOx as indicator) in the 100 most populated global cities, based on satellite NO2 data from the OMI instrument on the Aura satellite and gross urban product (GUP). This study was completed for the time period of 2005-2011 and demonstrated differences between those cities considered low-income and those denoted as high income cities with the later having decreasing NO2 due to air pollution controls despite economic growth (increasing GUP). The lower income cities had increasing NO2 with industrialization, urbanization, and increasing energy consumption indicative of rapid economic growth. This work can be expanded and improved in the future using NO2 observations from the recently launched ESA TROPOspheric Monitoring Instrument (TROPOMI), featuring even higher spatial resolution than OMI. More accurate estimates for NO2 emissions can be expected as well using the upcoming geostationary satellite instruments, such as the NASA Tropospheric Emissions: Monitoring of Pollution (TEMPO) and Korean Geostationary Environment Spectrometer (GEMS).

Data Sources:

This study uses Level-3 gridded NO2 VCD from OMI for 2005-2011 with a spatial resolution of 0.25 degree ×0.25 degree and a temporal resolution of 1 month, averaged to annual values, available from: NASA Earth Observing System Data and Information Services Center. GUP was calculated for 100 most populated urban areas using a combination of data from the Organization for Economic Cooperation and Development (OECD), United Nations (UN), and several other federal and state governments. The governments of China, Russia, Brazil, and state government of Maharashtra, India, self-reported data online on population, GUP, and/or GUP per capita for cities. The different organizations define the spatial unit “city” differently, but in all cases, GUP was compared with NO2 over the 13 × 13 km grid closest to the center of the city coordinates. ed courtesy of the Aura OMI science team.

References: Montgomery, A. and T. Holloway (2018). Assessing the relationship between satellite-derived NO2 and economic growth over the 100 most populous global cities, J. Appl. Rem. Sens., 12(4),