A glance at glowing plants with GOME-2

In a recent study I did with young researchers Erik van Schaik and Maurits Kooreman, we captured the faint glow emitted by plants when they are in the process of taking up carbon dioxide from the atmosphere. This glow is called solar induced fluorescence, and it is possible with EUMETSAT’s GOME-2 sensor on the MetOp-A satellite, to make global measurements.

Our new SIFTER (Sun-Induced Fluorescence of Terrestrial Ecosystems Retrieval) v2 algorithm improves over a previous version by using a narrower spectral window that avoids strong oxygen absorption. It was necessary to correct for degradation occurring in the GOME-2 instrument after 2013. Through correction, we generated stable, good-quality SIF retrievals for the entire data record from GOME-2, running from January 2007 until December 2019. We have already seen the first usage of our dataset to analyze the effects of heatwaves on vegetation growth and carbon uptake. The paper in Atmospheric Measurement Techniques can be found here.

The data is freely available at www.temis.nl, and via the following DOI:

SIFTER sun-induced vegetation fluorescence data from GOME-2A (Version 2.0) M. L. Kooreman, K. F. Boersma, E. van Schaik, R. van Versendaal, A. Cacciari, and O. N. E. Tuinder https://doi.org/10.21944/gome2a-sifter-v2-sun-induced-fluorescence

TROPOMI tracking NOx emissions day by day

It is now possible to track the NOx emissions from a city on a day-by-day basis, as long as there are no clouds obscuring the satellite’s field of view. Access the paper in Scientific Reports here. Or as tweeted by lead author Alba Lorente: daily measurements at high spatial resolution allows to estimate daily NOx emissions from megacities . The methodology of our latest study shows the potential of current&future sensors to detect emissions of air pollutants .

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This figure shows the tropospheric NO2 columns over Paris on Friday 23 February 2018 as observed by TROPOMI. The open circles represent the NO2 surface concentration in μg m−3 measured at urban background stations within 30 minutes of the TROPOMI overpass time (leftmost colour bar). The Paris A86 ring road is indicated by the inner black line, and the city limits are approximated by the outer black line. The right panel shows how NO2 accumulates over Paris along with the wind.

Ozone smog in hot Randstad

On Wednesday 24 July and Thursday 25 July 2019 the temperature will be very high. In combination with the intense sunlight and plenty of NOx and VOC emissions this is bound to lead to severe ozone smog over The Netherlands. Peaks of up to 200 microgram/m3 are expected in the west. See below the air pollution forecast for 23-24-25 July. Schermafbeelding 2019-07-23 om 17.09.33

Congratulations, Dr. Lorente!

On 23 May 2019, Alba Lorente succesfully defended her PhD-thesis titled ‘From photon paths to pollution plumes – better radiative transfer calculations to monitor NOx emissions with OMI and TROPOMI’ in the Aula of Wageningen University. Congratulations, Dr. Alba!

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We also hosted a mini-symposium on Satellite Measurements of Pollution and Climae to celebrate Alba’s accomplishment. As you can see above, there was joy and jubilation.

Date: 23 May 2019
Location: Campus Wageningen University, Atlas Building, Room 2

A mini-symposium on the occasion of the PhD defence of Alba Lorente.

14.00-14.05 Welcome. Chair: Folkert Boersma (WUR/KNMI)
14.05-14.25 TROPOMI discoveries from Belgium – Martine de Maizière (BIRA)
14.25-14.45 Clouds from space using oxygen absorption – Piet Stammes (KNMI)
14.45-15.05 Is TROPOMI of any use for Environmental Agencies? Guus Velders (Utrecht University, RIVM)
15.10-15.30 CH4 measurements from TROPOMI – Otto Hasekamp (SRON)
15.30-15.50 Remote sensing of deforestation without TROPOMI – Martin Herold (WUR)
15.00-16.00 Closing words Maarten Krol (WUR)

Abstract PhD-thesis:

Nitrogen oxides play an important role in atmospheric chemistry, affecting air quality and Earth’s radiative forcing, which impact public health, ecosystems and climate. Remote sensing from satellites results in measurements of tropospheric NO2 column densities with high spatial and temporal resolution. NO2 satellite retrievals have improved extensively in the last decade, together with the increased need of having traceable characterization of the uncertainties associated with the measurements. The resolution of the satellite instruments is improving such that the observed NO2 pollution can be traced back to emissions from individual cities. However, the uncertainty of satellite NO2 retrievals is still considerable and mainly related to the adequacy of the assumptions made on the state of the atmosphere. In this thesis we have improved the critical assumptions and our understanding in the radiative transfer modelling for NO2 satellite measurements, and we use TROPOMI NO2 measurements to quantify daily NOx emissions from Paris.

More information can be found here.

Aura OMI International Team Awarded USGS 2018 Pecora Award

The Ozone Monitoring Instrument (OMI) International Team, consisting of Dutch, Finnish and American scientists, was awarded the 2018 William T. Pecora Award by the United States Geological Survey. The Team includes everyone involved in data processing, retrieval algorithm development, and validation. The Pecora award is presented annually to recognize outstanding contributions by individuals or teams using remote sensing to understand the Earth, educate the next generation of scientists, inform decision makers or support natural or human-induced disaster response. It is sponsored by the U.S. Department of the Interior and NASA.


The figure above shows that OMI observed tropospheric NO2 reductions between 2006 and 2016 in most of western Europe, and increases in some parts of eastern Europe. Figure by Marina Zara and Folkert Boersma (KNMI, Wageningen University).


‘Improving algorithms and uncertainty estimates for satellite NO2 retrievals’ published in Atmospheric Measurement Techniques

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This study wraps up our long-term effort from the QA4ECV-project to generate an improved satellite NO2 dataset for the period from 1995 to 2017. The work was done with a strong consortium of European and international colleagues, and has led to what we believe is a substantially improved NO2 retrieval algorithm and dataset. The data is freely available through www.qa4ecv.eu and www.temis.nl.

The paper’s reference: Boersma, K. F., Eskes, H. J., Richter, A., De Smedt, I., Lorente, A., Beirle, S., van Geffen, J. H. G. M., Zara, M., Peters, E., Van Roozendael, M., Wagner, T., Maasakkers, J. D., van der A, R. J., Nightingale, J., De Rudder, A., Irie, H., Pinardi, G., Lambert, J.-C., and Compernolle, S. C.: Improving algorithms and uncertainty estimates for satellite NO2 retrievals: results from the quality assurance for the essential climate variables (QA4ECV) project, Atmos. Meas. Tech., 11, 6651-6678, https://doi.org/10.5194/amt-11-6651-2018, 2018.


Announcement: QA4ECV NO2 ECV precursor record (v1.1) released

The European QA4ECV consortium, consisting of KNMI, the University of Bremen, IASB-BIRA, Max Planck Institute for Chemistry, and Wageningen University, announces the public release of a full data set of nitrogen dioxide (NO2) columns from the GOME, SCIAMACHY, OMI, and GOME-2(A) sensors.

The QA4ECV NO2 Essential Climate Variable precursor product contains harmonized vertical NO2 columns for the period 1995-2017. The dataset contains three products: (1) the tropospheric vertical column density, (2) the stratospheric vertical column density, and (3) the total vertical column density. The NO2 ECV precursor data is available as Level 2 (orbital swath) data. In addition to vertical NO2 columns, the product contains intermediate results, such as the result of the spectral fit, fitting diagnostics, the averaging kernel, cloud information, and detailed algorithm and product uncertainty estimates. Also Level 3 (monthly mean) data products are made available, based on Level-2 data of good quality, binned and averaged on a 0.125° × 0.125° degree global grid.

The NO2 data set can be found via the QA4ECV project website:

www.qa4ecv.eu then click ECV DATA, or directly via www.qa4ecv.eu/ecv/no2-pre. That page also provides additional information on these data, including the Product Specification Document, an interactive algorithm Traceability Chain, and a User Forum.

The QA4ECV datasets are linked to a DOI (Digital Object Identifier) to enable direct referencing of the dataset, e.g. when using the dataset in a publication. The dataset format is netcdf.

OMI / EOS-Aura (2004-2017)

Boersma, K. F., Eskes, H., Richter, A., De Smedt, I., Lorente, A., Beirle, S., Van Geffen, J., Peters, E., Van Roozendael, M. and Wagner, T., (2017). QA4ECV NO2 tropospheric and stratospheric vertical column data from OMI (Version 1.1) [Data set]. Royal Netherlands Meteorological Institute (KNMI). http://doi.org/10.21944/qa4ecv-no2-omi-v1.1.

GOME-2 / METOP-A (2007-2016)

Boersma, K. F., Eskes, H., Richter, A., De Smedt, I., Lorente, A., Beirle, S., Van Geffen, J., Peters, E., Van Roozendael, M. and Wagner, T., (2017). QA4ECV NO2 tropospheric and stratospheric vertical column data from GOME-2A (Version 1.1) [Data set]. Royal Netherlands Meteorological Institute (KNMI). http://doi.org/10.21944/qa4ecv-no2-gome2a-v1.1


Boersma, K. F., Eskes, H., Richter, A., De Smedt, I., Lorente, A., Beirle, S., Van Geffen, J., Peters, E., Van Roozendael, M. and Wagner, T., (2017). QA4ECV NO2 tropospheric and stratospheric vertical column data from SCIAMACHY (Version 1.1) [Data set]. Royal Netherlands Meteorological Institute (KNMI). http://doi.org/10.21944/qa4ecv-no2-scia-v1.1

GOME / ERS-2   (1995-2002)

Boersma, K. F., Eskes, H., Richter, A., De Smedt, I., Lorente, A., Beirle, S., Van Geffen, J., Peters, E., Van Roozendael, M. and Wagner, T., (2017). QA4ECV NO2 tropospheric and stratospheric vertical column data from GOME (Version 1.1) [Data set]. Royal Netherlands Meteorological Institute (KNMI). http://doi.org/10.21944/qa4ecv-no2-gome-v1.1

Ozone smog formation over Europe sensitive to NOx reductions

Our satellite data of tropospheric NO2 from OMI have contributed to a study showing that over the last 12 years, cities in North America, Europe and East Asia, are more often VOC-limited or in a transitional state between VOC and NOx-limited. For instance, in 2005 Amsterdam’s ozone production during Summer was limited by VOCs, but by 2015 it had transitioned to a NOx-limited system due to reduced NOx emissions resulting from controls put into place at both regional and national levels. This transition means that future NOx reductions should further decrease ozone summer smog in Europe. For a NASA press release on the study, click here.

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TropOMI launched, on, and detecting NO2

On Friday, 13 October 2017 the Dutch design TropOMI instrument was launched into an 800 km altitude orbit from Plesetsk, Russia. The instrument was switched on on 18 October. It works! Click here for a short movie of the launch and turn those woofers up :-)!

‘First light’ has arrived at the detectors (6 November 2017). TROPOMI’s CCD detectors are still quite warm, but the instrument nevertheless appears capable of recording light levels that at first glance seem to make geophysical sense. Now waiting for the coolers to start their heat transfer to outer space, and reduce that dark current in the detectors. So far, so good!

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Picture of the Month: A still from the TropOMI (Sentinel-5P) liftoff on a Rockot from the Plesetsk Cosmodrome in northern Russia at 09:27 GMT (11:27 CEST) on 13 October 2017.

If you want to read more on ow TropOMI is doing in the so-called commissioning phase, check out this website: https://tropomi.wordpress.com. Some other first signs of success have been reported on Dutch Public News Outlets (NOS, click here).

For our plan on how to retrieve NO2 from TROPOMI, please click here.