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.


Structural uncertainty in air mass factors paper selected as EGU Highlight article

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The study led by my PhD-student Alba Lorente and supported by the QA4ECV-team focuses on AMF structural uncertainty, by comparing the AMF calculation approaches by seven different retrieval groups and providing a traceable analysis of all components of the AMF calculation.

Summary: Choices and assumptions made to represent the state of the atmosphere introduce an uncertainty of 42% to the air mass factor calculation in trace gas satellite retrievals in polluted regions. The AMF strongly depends on the choice of a priori trace gas profile, surface albedo data set and the correction method to account for clouds and aerosols. We call for well-designed validation exercises focusing on situations when AMF structural uncertainty has the highest impact on satellite retrievals.

Clicking the picture above takes you to the journal website where the paper can be downloaded.

Improved OMI NO2 record (2004-2015) from the EU QA4ECV project

schermafbeelding-2017-03-02-om-21-22-33One of the prime targets of the EU-project Quality Assurance for Essential Climate Variables (QA4ECV, www.qa4ecv.eu) is the generation and subsequent quality assurance of harmonized, long-term data records of Essential Climate Variables (ECVs) or precursors thereof. We have recently generated an improved retrieval algorithm for NO2 columns and its application to spectra measured by the OMI sensor over the period 2004-2015. Our community ‘best practices’ algorithm is based on the classical 3-step DOAS method. It benefits from a thorough comparison and iteration of spectral fitting and air mass factor calculation approaches between IUP Bremen, BIRA, Max Planck Institute for Chemistry, KNMI, WUR, and a number of external partners. Version 1 data is currently being evaluated but already available here (click Data Access) and more information on the retrieval algorithm can be found by clicking Traceability Chain. We will present this new OMI NO2 satellite product, its strengths and weaknesses at this year’s EGU-meeting in Vienna.

Substantial structural uncertainty in AMF calculations

schermafbeelding-2016-11-02-om-10-46-47In this paper in Atmospheric Measurement Techniques Discussions we quantify the structural uncertainty that arises when different air mass factor (for NO2 and HCHO) methodologies are applied for the same satellite observations. Theoretical uncertainty (also known as parametric uncertainty) is the uncertainty arising within one particular retrieval method. Structural uncertainty is the uncertainty that arises when different retrieval methodologies are applied to the same data (Thorne et al., BAMS, 2005). The study led by Alba Lorente focuses on AMF structural uncertainty, by comparing the AMF calculation approaches by seven different retrieval groups and providing a traceable analysis of all components of the AMF calculation. The above picture shows the ratio of NO2 AMFs calculated by 7 different groups to the ensemble mean AMFs for polluted and unpolluted situations over China.

Agricultural practices pollute Chinese air

Schermafbeelding 2016-09-01 om 08.53.23Our satellite measurements helped to show that the burning of crop residues in China causes a lot of air pollution on top of the already strong emissions from industry and traffic there. The study lead by our colleagues from the Belgian Institute for Space Aeronomy indicates that the top-down crop burning fluxes of volatile organic compounds in June exceed by almost a factor of 2 the combined emissions from other anthropogenic activities in this region, underscoring the need for targeted actions towards changes in agricultural management practices. Read more about the study here.

See the news item of Wageningen University on the paper by clicking this link.schermafbeelding-2016-09-13-om-14-44-20.