NO2 & SO2


Nitrogen dioxide over Bucharest (Source: University of Bremen/University of Galati)



Component products

Air Quality


  • N/A



  • Environmental monitoring – Continuous monitoring of changes throughout the lifecycle

Geo-information requirements

  • Air quality and emissions



This product provides measurements of gas concentrations such as tropospheric NO2 and SO2, which are indicator of the overall pollution of an area.

A typical air quality forecast delivers maps of air pollution, including nitrogen dioxide and sulphur dioxide, in a region or local authority as a public information service. The products usually have either high resolution dispersion models or moderate resolution chemical transport models (CTMs) at their heart.  These models have spatial resolutions of a few hundred meters (dispersion) and a few km (CTM).  Both use current meteorology data (weather forecasts) and available local or regional emission datasets, with boundary conditions obtained from global models.  Very accurate dispersion models based on computational fluid dynamics are developed In selected cases (airports, city centres) to account for the detailed effects of individual buildings and pollution build up along major roads with tall buildings – “street canyons”.  Because tropospheric transport is very complex, CTM models are limited to averages over a few square km. 

The upcoming Sentinel-4 mission covers the need for continuous monitoring of the atmospheric chemistry at high temporal and spatial resolution. Main data products will be O3, NO2, SO2, HCHO and aerosol optical depth, which will be generated with high temporal resolution (~ 1 h) to support air quality monitoring and forecast over Europe.

The upcoming Sentinel-5 Precursor mission is expected to provide measurements of ozone, NO2, SO2, BrO, formaldehyde and aerosol.

Known restrictions / limitations

Apart from the availability of ground-based data for best accuracy and resolution, drawbacks associated with EO for NO2 and SO2 assessment are the spectral interferences caused by atmospheric components that are not pollution, e.g. water vapour or secondary aerosols from natural sources.

Satellite observations are made only in specific wavelength ranges and the results of the observations are subject to the atmospheric conditions. Pollutants with a low concentration will usually not be detected. Another constraint is the need for highly qualified staff to supervise the process.

Lifecycle stage and demand












  • To provide accurate baseline air quality scenario.

Development & Production:

  • Information to minimise the amount of emissions, and gas flared or vented to the environment.
  • Information to monitor impacts on the environment and highlight good and bad performers.

Geographic coverage and demand

Demand and coverage is global.

Challenges Addressed

OTM:021 Air quality (emissions) monitoring

HC:4106 Air quality monitoring on an airshed and site specific basis


Input data sources


  • EOS-Aura OMI
  • METOP-A GOME-2 (2006–present (NO2) 2012–present (SO2))                                                                                                                                                                                                                                                                                                                                                                                                       


  • ERS-2GOME (1996-2003)
  • ENVISAT SCIAMACHY (2002–2012)


  • Sentinel-4, Sentinel-5

Supporting data:

  • Ground-based measurements

Spatial resolution and coverage

Spatial resolution:

  • EOS-Aura OMI: spatial resolution varies significantly with track position. mean spatial resolution of 13 x 24 km
  • METOP-A GOME-2:  80 km x 40 km
  • ERS-2 GOME: 40 x 40 km to 40 x 320 km
  • ENVISAT SCIAMACHY: 32 x 215 km

Minimum Mapping Unit (MMU)


Accuracy / constraints

Thematic accuracy: N/A

Spatial accuracy: N/A

Accuracy assessment approach & quality control measures

In all carbon dioxide emission retrieval programs, ground measurement sites play a critical role in evaluating satellite data and retrieval models; targeted aircraft campaigns can also provide verification and better understanding of source regions.

Frequency / timeliness

Observation frequency:

  • EOS-Aura OMI: daily, nearly global coverage
  • METOP-A GOME-2: Global coverage can be achieved within one day
  • ERS-2 GOME: daily
  • ENVISAT SCIAMACHY: Global monthly mean maps are available from January 2003 to April 2012

Timeliness of deliverable: Following model development and calibration, products are made available immediately, e.g. on a monthly basis.


If freely available or commercially acquired is depending on the selected sensor.

Delivery / output format

Data type:

  • Vector formats

Format by sensor:

  • METOP-A GOME-2: Granule products are available as imagery (gif), binary or BUFR. Daily products (1 x 1.25 deg maps) are available in ASCII or GRIB2 format.
  • ENVISAT SCIAMACHY: mixed-binary format


Download product sheet.


Lead Author:


Peer Reviewer:



Maria Lemper; Jan Militzer

Document Title:

NO2 & SO2

# of Pages:



Internal – Project consortium and science partners


External – ESA

This page has no comments.