TROPOMI NO2 data version overview

Tropospheric NO2

Note: the vertical dashed line marks a change in the along-track ground pixel size; this change did not lead to a change in the version number.

The TROPOMI NO2 data processor occasionally undergoes version updates, shown above as vN.M.x (where the last digit is for minor bug fixes only). The collection number (left most numbers) is currently linked to the version of the level-1b (ir)radiance spectra.

The initial operational processing started in May 2018 and constitutes versions v1.M.x, followed by v2.2.0 after updates of the level-1b data.

To harmonise the NO2 data, there was an intermediate reprocessing on the PAL system with version v2.3.1, up to the operational processing of that version. This dataset was published in December 2021, but is no longer available.

After further updates of the level-1b data and the NO2 processor, the current version is v2.4.0 -- this version is used for a full mission reprocessing up to the operational switch to v2.4.0, which replaces all previous versions.

Version v2.5.0 implements a small bug fix in the OFFL code. The change only affects the qa_value field in the datafiles over snow or ice covered regions; the update makes OFFL consistent with NRTI & RPRO v2.4.0 and the ATBD. A recipe to update OFFL v2.4.0 to v2.5.0 is given below.

For version v2.6.0 the NO2 algorithm itself is exactly the same as v2.5.0. There was, however, an issue fixed in the FRESCO cloud algorithm (see the Product User Manual & Product ReadMe File) which has unintended effects on the cloud pressure and therefore on the air-mass factor calculations in the NO2 algorithm; in v2.7.1 the change in FRESCO is rolled back. Users are adviced to use NO2 data from v2.6.0 with care.

In version v2.7.1, an FRESCO issue fixed in v2.6.0 is rolled back, as it had unintended effects on the NO2 calculations. At the same time several improvements have been implemented: a new surface albedo climatology, adaptations in the qa_value reduction factors, a new digital elevation map (DEM) for the surface elevation, and extra diagnostic data variables (see the Product User Manual & Product ReadMe File).

collection	version	type	start date start orbit	end date end orbit	dataset DOI
Obsolete versions:
01	v1.M.x	OFFL RPRO	30 April 2018 02818	01 July 2021 19257	10.5270/S5P-s4ljg54
02	v2.2.0	OFFL	01 July 2021 19258	14 Nov. 2021 21187	10.5270/S5P-9bnp8q8
	v2.3.1	OFFL	14 Nov. 2021 21188	17 July 2022 24654	10.5270/S5P-9bnp8q8
PAL	v2.3.1	PAL_	01 May 2018 02832	14 Nov. 2021 21187	N/A
Versions to be used:
03	v2.4.0	RPRO	01 May 2018 02832	25 July 2022 24779	10.5270/S5P-9bnp8q8
		OFFL	17 July 2022 24655	12 March 2023 28030	10.5270/S5P-9bnp8q8
		The recommendation is to use the RPRO data up to the end and only then switch to the OFFL data, so as to avoid spin-up issues at the beginning of the OFFL data stream.
	v2.5.0	OFFL	12 March 2023 28031	26 Nov. 2023 31704	10.5270/S5P-9bnp8q8
	v2.6.0	OFFL	26 Nov. 2023 31705	08 Sep. 2024 35777	10.5270/S5P-9bnp8q8
		Use NO2 data from v2.6.0 with care; see remark above.
	v2.7.1	OFFL	08 Sep. 2024 35778	TBD	10.5270/S5P-9bnp8q8

Examples of names of NO2 orbits:

   S5P_RPRO_L2__NO2____20180901T013259_20180901T031627_04578_01_010202_20190220T132149.nc
   S5P_PAL__L2__NO2____20180901T013358_20180901T031528_04578_01_020301_20211108T224129.nc
   S5P_OFFL_L2__NO2____20210901T004236_20210901T022405_20127_02_020200_20210902T174110.nc
   S5P_RPRO_L2__NO2____20220725T170921_20220725T185050_24776_03_020400_20230203T050713.nc
   S5P_OFFL_L2__NO2____20220821T220529_20220821T234658_25162_03_020400_20220825T083000.nc
       type            start_date      end_date        orbit CN vers.  production_date

where:

• type is the processing type:
  • OFFL for official offline processing
  • RPRO for official reprocessing
  • PAL_ for the PAL reprocessing
  • NRTI for the near-real time processing -- not included here
• start_date and end_date specify the begin and end data & time of the orbit
• orbit is the orbit number (5 digits)
• CN is the collection number (2 digits)
• vers. is the NO2 data version (6 digits)
• production_date is when the orbit file was made

 

Recipe to update OFFL v2.4.0 to v2.5.0

Full quote from the Product ReadMe File regarding this update reads:

The version 02.05.00 NO2 product implements a small bug fix in the OFFL code. The change only affects the qa_value field in the datafiles, and only over snow or ice covered regions. In the corrected OFFL version there are more pixels that receive a qa_value > 0.75, in case the scene pressure over snow/ice matches the surface pressure to within 4% (was 2% in previous versions). The OFFL 02.04.00 code, operational since 17 July 2022, did not receive this latest change. The update makes OFFL consistent with NRTI, RPRO v02.04.00 and the ATBD.

The data user can adjust the qa_value of OFFL v2.4.0 by following this recipe:

    if ( 0.50 < qa_value_v240 < 0.75 ) then
      if ( 80 < snow_ice_flag < 104 ) then
        if ( 0.96 <= apparent_scene_pressure / surface_pressure <= 0.98 ) then
          qa_value_v250 = qa_value_v240 * 0.88 / 0.73

where 0.88 (0.73) is the qa_value multiplication factor for cases where the ratio between the scene and surface pressure is >0.96 (<0.96) in the bug-fixed data version -- in the OFFL v2.4.0 the limit was incorrectly set at 0.98.

 

TROPOMI NO2 data version documentation

• See the NO2 data products page for the latest available version of:
  • Algorithm Theoretical Basis Document [ATBD]:
    van Geffen, J.H.G.M., Eskes, H.J., Boersma, K.F., Maasakkers, J.D. and Veefkind, J.P., TROPOMI ATBD of the total and tropospheric NO2 data products, Report S5P-KNMI-L2-0005-RP, KNMI, De Bilt, The Netherlands.

  • Product User Manual [PUM]:
    Eskes, H., van Geffen, J., Boersma, F., Eichmann, K.-U., Apituley, A., Pedergnana, M., Sneep, M., Veefkind, P.J. and Loyola, D., Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Nitrogen Dioxide, Report S5P-KNMI-L2-0021-MA, KNMI, De Bilt, The Netherlands.

  • Product ReadMe File [PRF]:
    Eskes, H. J. and Eichmann K.-U., S5P MPC Product Readme Nitrogen Dioxide, Report S5P-MPC-KNMI-PRF-NO2, ESA.

• Van Geffen, J.H.G.M., Eskes, H.J., Compernolle, S., Pinardi, G., Verhoelst, T., Lambert, J.-C., Sneep, M., ter Linden, M., Ludewig, A., Boersma, K.F. and Veefkind, J.P.,
  Sentinel-5P TROPOMI NO2 retrieval: impact of version v2.2 improvements and comparisons with OMI and ground-based data, Atmos. Meas. Tech. 15, 2037-2060, doi:10.5194/amt-15-2037-2022, 2022.

• The v2.3.1 intermediate reprocessing on the PAL system is described in a separate PAL NO2 readme file. The dataset is no longer available since it is superseded by the official reprocessing (RPRO) dataset based on v2.4.0 and following versions.

 

Download of TROPOMI NO2 data

• The official download point is the Copernicus Data Space Ecosystem
• ESA's S5P-PAL Data Portal hosts several pre-operational TROPOMI retrieval products.
• The officially released data can also be found at NASA's GES DISC Data Collections portal; the PAL data is not included there
• The v2.4.0 (and following) OFFL and RPRO data can be found at TEMIS's Tropospheric NO2 columns from satellite page in a volume-reduced version as daily .tar files; the qa_value of v2.4.0 OFFL files have been updated as described with the above recipe.

last modified: 20 November 2024
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