New paper published! – OMI aerosol height over land from the O2-O2 visible absorption band, based on neural networks


Retrieving aerosol height from passive satellite sensors providing then daily global observations of our atmosphere is a very important issue and a burning challenge. This is very important for air quality and climate purposes, but also for better correcting the aerosol scattering effects present in the spectra measurements when quantifying the atmospheric trace gas amounts (e.g. NO2, CH4, CO2, etc…).

For the first time, we have developed an algorithm devoted to the OMI 477 nm O2-O2 measurements and applied it over land surfaces. The employed approach relies on machine learning (cf. neural network) approach. The obtained product shows encouraging results with uncertainty below 800 m.

These results are now published in the Atmospheric Measurement Techniques (AMT) peer-review journal.

Great thanks to all the co-authors KNMI and the GRS research department for their support on this very nice study!

More details can be read here, and paper available here.

For sure, more results to come in a near future…

New page CO – Carbon Monoxide!

A new page hast been created in the “Atmosphere composition” section: CO – Carbon Monoxide.

What is CO? How is CO produced? Why shall we observe atmosphere CO? A typical CO satellite map? Some reference CO satellite missions / products?

If you are interested, you can find some answers here. Do not hesitate to comment or ask for more questions, via Twitter or the contact form!

Homepage promotion in the SNELLIUS newsletter!


SNELLIUS, the Master student association of the Geoscience & Remote Sensing (GRS) track, asked me to write an article about my new website, and the reasons behind this.

If you are interested, you can read it here:

Many thanks to them for giving me this opportunity!

More information about the SNELLIUS association here.

EU concerned about air and water pollution: an example with the Netherlands

Extracted from

When mentioning the term “pollution”, we usually think about China or India. And yet, European states are not exempt from some issues. Even in the Netherlands…

In its last Environmental Implementation Review Country Report, the European commission has recommended us to improve water (nutrient concentrations of nitrogen and phosphorus due to Eutrophication) and air quality (NO2 and O3). One of the main reasons is the traffic. Major metropolitan cities like Rotterdam, Amsterdam and The Hague were all in the top 12 worst cities for traffic congestion and pollution within EU.

For the year 2013, the European Environment Agency estimated that about 11,530 premature deaths were attributable to fine particulate matter concentrations, with an additional 270 to ozone concentration and over 1,820 to nitrogen dioxide.

In spite of all these warnings, “The Netherlands has long been a leader in environmental policy, and scores very well when it comes to compliance with the EU rules on drinking water quality and waste water treatment.” (cf. EU Environmental Commissioner Karmenu Vella).

What can we do then? To reduce pollutant emissions, traffic rush hour, to continue to lead the various green initiatives and to pay more attention to national nature works.


More information on &


Successful & inspiring Urban Air Quality Symposium in Delft

Public audience at the Urban Air Quality symposium on 2017.02.17 (photo taken by Debbie Rietdijk)

On Friday 2017.02.17, the TU Delft Climate Institute, the Geoscience & Remote Sensing (GRS) research department and the Dutch Meteorological Institute (KNMI) were honoured to host the Urban Air Quality symposium in Delft, at the Theaterzaal (Sport & Culture).

Thanks to a broad audience of 90 people attending this event, 9 invited speakers from space agency (ESA), research institutes (DCMR, RIVM, KNMI), company (TNO) and universities (UU, WUR, TU Delft), and an inspiring interactive discussion of ~30 minutes at the end between the public and the guests, this symposium was a great success!

Among many elements, the following issues and topics were emphasized:

  • Not only fine particles (such as PM2.5) affect human health and contribute to air quality declination, but gases such as NO2 itself is very harmful. Long-term exposure affects our lifetime but also our life quality…
  • The Netherlands has a unique set of technical skills about air quality monitoring in urban area, combining satellite instruments (OMI & TROPOMI) and ground-based infrastructures. Such competences are an asset and provide a high value of data and information to the society.
  • Developments of small air quality sensors are now in progress to improve measurements of air quality at the “nose level”. Such information is still hard to have over the whole globe and with fine spatio-temporal resolution.
  • Deriving surface emissions either from observations or by statistic means is clearly one of the biggest challenge for the next years. A lot of information are now made available but uncertainty characterization remains complex.
  • Improving our air quality environment is urgent not only for our health but also for improving our life style (e.g. stress). But this requires drastic changes in our individual daily life and actions.
  • Communication to society remains a challenge as each individual data  plot can be interpreted in different ways by the public. Diverse and innovative communication supports should be provided and further worked in addition to the classical ones.
  • Satellite observation can clearly provide trends on our air quality. But we need to pay attention to their interpretations: for example a decrease of air pollutants over 10 years does not mean this increase has been continuous and regular. OMI NO2 data show clear increase of NO2 over China until 2010, but a decrease has started then afterwards.

Interested to know more?  Please have a look on our GRS, KNMI or the TU Delft Climate Institute websites and our partners. Or contact us!

We take the opportunity to thank a lot all the 9 speakers who immediately accepted our invitations (Gerard Hoek – UU, Sef van den Elshout  – DCMR, Yasjka Meijer – ESA, Folkert Boersma – KNMI-WUR, Henk Eskes – KNMI, Hugo Denier van der Gon – TNO, Jieying Ding – TU Delft-KNMI, Guus Velders – RIVM, Ernst Meijer – TNO), the co-organisors and co-chairmen (Pieternel Levelt, Pepijn Veefkind, Julien Chimot, Tim Vlemmix), Debbie Rietdijk for the helpful material and practical supports, Jiyunting Sun for the flyer advertisement, Herman Russchenberg for the idea and everyone present in the audience.

We will likely repeat this initiative in the future!


A large SO2 pollution in Iraq observed from space

OMI SO2 (DU) over Iraq in 2016.10.24 (Source:
MODIS true color image of 2016.10.24 – Aerosol plume in Iraq following the fire from the sulphur facility (Source: htt[://

Sometimes, atmospheric satellite observations and reality are combined together delivering then measurements of a sad reality…

This is the case with this map of SO2 (sulphure dioxide) pollution retrieved from OMI (cf. Nikolay Krotkov). This tremenduous pollution is caused by a fire, in October 2016, at the Al-Mishraq sulphur facility. It could be then monitored in almost real time. Because it stayed in the first days close to the surface, two people died and up to 1000 have been treated for breathing problems.

The white-gray colour, as depicted by MODIS sensor, illustrates the presence of sulfate aerosols and droplets of sulfuric acid. Both components highly reflect the sun light. The black carbon from the Oayyarah oil field lead to a black smoke, as these particles absorb light.

Note a similar fire was already identified 13 years ago by atmospheric scientists at NASA’s Goddard Space Flight Center and the University of Maryland, Baltimore County. It released 21 kilotons of toxic sulfur dioxide per day.

More information here.


President Obama explains how air pollution affects our planet


Some months ago, the air quality satellite community was very glad to discover (a bit by surprise) this movie where president Barack Obama explained the issues related to air quality. As an additional surprise, pictures of the OMI EOS-Aura satellite (NO2 maps over China and USA) were shown to support his statements.

This is a great honour as scientists spent, at least the last 10 years, to convince politicians of the high value of satellite measurements regarding our atmosphere and how they can support relevant emission regulation policies.

The movie can be visualised on youtube here.

Will the next 45th American president continue in that direction?

New UNICEF report – Clear the air for children

The new UNICEF report (October 2016) addresses the last and very concerning numbers about children and the air quality in the world. Overall,

  • Around 2 billion children live in areas where outdoor air quality exceeds international limits
  • 300 million children live in areas with pollution above 6 times international limits
  • In Europe, between 20 and 120 million are living in areas where outdoor air quality exceeds up to 2 times international limits


This is a very good document, well written and easy to read. More information here:



Urban Air Quality symposium in Delft – 2017.02.17

Save the date!!

The Geoscience Remote Sensing (GRS) department of TU Delft, the TU Delft Climate institute and the Royal Netherlands Meteorological institute KNMI are pleased to invite you to the seminar Urban Air Quality, to be held at the TU Delft Theaterzaal (Sports & Camp; Culture) on Friday afternoon 17th February 2017.

It targets a broad audience from students in diverse topics, public, industries, policy makers and researchers.

Read more in the programme below and here:

Please register by sending an email to


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