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

SCIAMACHY / ENVISAT (2002-2012)

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

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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.