Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

SPASCIA Presentation: Analysis of NO2 from S5P Tropomi for monitoring

How COVID-19 is impacting on pollution levels over European cities?
Considering the very peculiar times we are living in, SPASCIA has taken the opportunity of its current use of Sentinel 5 Precursor (S5P) data and products within the PHIDIAS project to analyse the time evolution of atmospheric pollution. The aim has been to tentatively assess the impact of the exceptional human activity reduction due to the COVID-19 crisis on atmospheric pollution levels over some major cities in Europe.

  • Be the first to comment

  • Be the first to like this

SPASCIA Presentation: Analysis of NO2 from S5P Tropomi for monitoring

  1. 1. 1 SPASCIA Introduction Analysis of NO2 from S5P TROPOMI for monitoring pollution level at city scale SPASCIA Pascal Prunet, Olivier Lezeaux, Claude Camy-Peyret, Hervé Thevenon Work supported by PHIDIAS Work supported by AERIS/ICARE and CNES
  2. 2. 2 SPASCIA Project objectives1-SLIDE SUMMARY ➢ From ESA S5P measurements of the air pollutant NO2 from space, we have assessed the impact of the human activity reduction on air pollution by comparing the first trimester periods of 2019 and 2020 on a daily, weekly and monthly basis for 4 major cities in Europe ➢ Reductions in the pollution level (using NO2 as a proxy) have been observed at the end of March 2020 (20-50% for Paris; 30-70% for Milan region; 30-60% for Madrid; 40-60% for the last week for Athens), as compared to the same period in 2019 PARIS 2019 15-31 March averages MILAN MADRID ATHENS 2020 15-31 March averages
  3. 3. 3 SPASCIA Project objectivesOBJECTIVE AND DATA ➢ We have assessed the impact of the human activity reduction on air pollution from ESA S5P TROPOMI high spatial resolution measurements of the pollutant NO2 by comparing the first trimester periods of 2019 and 2020 on a daily, weekly and monthly basis (whenever possible), for 4 major cities in Europe i.e. Paris, Madrid, Athens and Milan (within the Po valley area) ➢ We use the TROPOMI NO2 tropospheric column Level 2 product distributed by the European Space Agency (ESA) downloaded from the Copernicus open data access hub (https://s5phub.copernicus.eu) by the ICARE/AERIS French data centre (ftp.icare.univ-lille1.fr) imported and arranged at SPASCIA in a database (Postgresql 11.6, PostGIS 3.0 3) We generated data images centered on 4 cities and 2 periods of 3 months: from January to March 2019 and 2020 S5P L2 NO2 pixels are filtered each day : quality assurance value higher than 0.5, cloud fraction below 40%
  4. 4. 4 SPASCIA Project objectivesDEDICATED PROCESSING AT CITY SCALE ➢ Dedicated processing of daily samples at city scale Consider filtered pixels within a disk of 240 km diameter (Paris, Athens), 300 km diameter (Madrid), or 500 km diameter (Milan) Identify “valid” pixels (Figure 1a) : filtered pixels plus the spatial interpolation of the missing pixels where and when it is possible : if the position of this missing pixel is surrounded by at least 3 neighbouring filtered pixels Select daily datasets only when valid pixels are higher than 80% Total NO2 mass of the plume : integrating only the valid pixels higher than a background value (Figure 1b) Uncertainty : difference between the total NO2 mass and that for smaller disk (75% of the nominal size) (Figure 1c) 1a : interpolated (valid) pixels 1b : valid pixels above background for NO2 plume mass 1c : smaller pixel for uncertainty
  5. 5. 5 SPASCIA Project objectivesRESULTS : PARIS ➢ Examples of daily maps of NO2 tropospheric columns over Paris area for the end of March 2019 (top) and same days for the March 2020 (bottom) Only 33% of valid days on the January-March periods (frequent cloudy data) 19/03/2019 19/03/2020 26/03/2019 26/03/2020 30/03/2019 30/03/2020 31/03/2019 31/03/2020
  6. 6. 6 SPASCIA Project objectivesRESULTS : PARIS Qualitative comparison of AirParif estimates with S5P NO2 daily maps for 19 March ➢ Daily maps suggest pollution level reductions consistent with independent estimates. But weakly/monthly averages are required for reliable results AirParif NO2 pollution quantification from 17th to 19th March in normal situation and confined situation S5P data of NO2 tropospheric column over Paris region, 19th March 2019 (left) and 19th March 2020 (right)
  7. 7. 7 SPASCIA Project objectivesRESULTS : PARIS ➢ 15-day average and weekly average time series of total NO2 plume mass from January to March 2019 and 2020 Lack of valid data for building reliable averaged quantities in some periods Large temporal variability of uncertainty bars in January and February, possibly due to the impact of local meteorology and atmospheric transport when computing averages based on small numbers of daily values Robust averages available for mid-March periods Dates of 15-day periods from 01 January to 31 March Bi-weekly (15-day) averages of NO2 plume mass Weekly (7-day) averages of NO2 plume mass Dates of 7-day periods from 01 January to 31 March
  8. 8. 8 SPASCIA Project objectivesRESULTS : PARIS ➢ Monthly averaged maps of tropospheric NO2 column for 2019 and 2020 Comparisons for January suffer from reduced number of valid data in 2019 Comparisons for March appear more reliable January February March 2019 2020
  9. 9. 9 SPASCIA Project objectivesRESULTS : PARIS ➢ Robust results for second half of March show evidence of NO2 level reduction from 2019 to 2020 Comparison of 15-31 March averaged maps of NO2 tropospheric column A 20-50% reduction of the NO2 pollution level at the end of March 2020 is observed, as compared to the same period in 2019 Average on 15-31 March 2019 8 daily values Average on 15-31 March 2020 10 daily values
  10. 10. 10 SPASCIA Project objectivesRESULTS : MILAN AND PO VALLEY ➢ Examples of daily maps of NO2 tropospheric columns over Milan and Po valley region for the end of March 2019 (top) and 2020 (bottom) 50-70% of valid days on the January-March periods allow to derive reliable averages 16/03/2019 16/03/2020 21/03/2019 21/03/2020 24/03/2019 24/03/2020 28/03/2019 28/03/2020
  11. 11. 11 SPASCIA Project objectivesRESULTS : MILAN AND PO VALLEY ➢ 15-day average and weekly average time series of the total NO2 plume mass from January to March 2019 and 2020 Temporal variability in year-to-year differences from January to early March Trends of decreasing NO2 levels from early February to end of March observed both in 2019 and 2020 NO2 level reduction from 2019 to 2020 starting from mid-March Dates of 15-day periods from 01 January to 31 March Bi-weekly (15-day) averages of NO2 plume mass Weekly (7-day) averages of NO2 plume mass Dates of 7-day periods from 01 January to 31 March
  12. 12. 12 SPASCIA Project objectivesRESULTS : MILAN AND PO VALLEY ➢ Monthly averaged maps of tropospheric NO2 column for 2019 and 2020 Year-to-year comparisons are reliable for the 3 months and show a NO2 pollution level reduction starting in March 2020 as compared to 2019 January February March 2019 2020
  13. 13. 13 SPASCIA Project objectivesRESULTS : MILAN AND PO VALLEY ➢ Robust results for second half of March showing evidence of a significant NO2 level reduction from 2019 to 2020 A reduction of NO2 pollution level of 30 % over the second half of March 2020, as compared to the same period in 2019, is observed from these data The average data for the three last weeks of March suggests an increasing reduction with time, from about 20% (12-18/03 values) to about 65% (19-25/03 and 26-31/03 values) Average on 15-31 March 2019 15 daily values Average on 15-31 March 2020 9 daily values
  14. 14. 14 SPASCIA Project objectivesRESULTS : MADRID ➢ 15-day average and weekly average time series of total NO2 plume mass from January to March 2019 and 2020 Trends of decreasing NO2 levels from early February to end of March observed both for 2019 and 2020 NO2 level reduction from 2019 to 2020 from mid-March A large uncertainty in some case (e.g. 19-25 March 2020) is due to the small number of valid days for this period Dates of 15-day periods from 01 January to 31 March Bi-weekly (15-day) averages of NO2 plume mass Weekly (7-day) averages of NO2 plume mass Dates of 7-day periods from 01 January to 31 March
  15. 15. 15 SPASCIA Project objectivesRESULTS : MADRID ➢ Monthly averaged maps of tropospheric NO2 column (linear scale) for 2019 and 2020 Year-to-year comparisons are reliable for the 3 months : NO2 pollution level reduction in March 2020 as compared to 2019 is clearly observed January February March 2019 2020
  16. 16. 16 SPASCIA Project objectivesRESULTS : MADRID ➢ Robust results for second half of March show evidence of NO2 level reduction from 2019 to 2020 A reduction of NO2 pollution level of 10-30 % over the second half of March 2020, as compared to the same period in 2019, is observed from these data The average data for the last week of March suggests an even larger reduction of about 40-60 % (26-31/03 values) Average on 15-31 March 2019 15 daily values Average on 15-31 March 2020 5 daily values
  17. 17. 17 SPASCIA Project objectivesRESULTS : ATHENS ➢ 15-day average and weekly average time series of total NO2 plume mass from January to March 2019 and 2020 No evidence of noticeable NO2 level reduction from 2019 to 2020 in March from 15- day averages The NO2 mass reduction from 2019 to 2020 appears significant for the last week of March Dates of 15-day periods from 01 January to 31 March Bi-weekly (15-day) averages of NO2 plume mass Weekly (7-day) averages of NO2 plume mass Dates of 7-day periods from 01 January to 31 March
  18. 18. 18 SPASCIA Project objectivesRESULTS : ATHENS ➢ Monthly averaged maps of tropospheric NO2 column (linear scale) for 2019 and 2020 Year-to-year comparisons are reliable for the 3 months : No evidence of NO2 pollution level reduction in March 2020 as compared to 2019 January February March 2019 2020
  19. 19. 19 SPASCIA Project objectivesRESULTS : ATHENS ➢ Robust results for last week of March suggest NO2 level reduction from 2019 to 2020 The NO2 mass reduction from 2019 to 2020 appears significant for the last week of March, suggesting a beginning of the reduction of about 40-60 % (26-31/03 values) of NO2 levels for this period in 2020 as compared to 2019 The number of valid days available over the Athens area for the last two weeks of March 2019 and 2020 allows to be reasonably confident in this estimate Average on 23-31 March 2019 7 daily values Average on 23-31 March 2020 8 daily values
  20. 20. 20 SPASCIA Project objectivesSUMMARY ➢ From ESA S5P measurements of the air pollutant NO2 from space, we have assessed the impact of the human activity reduction on air pollution by comparing the first trimester periods of 2019 and 2020 on a daily, weekly and monthly basis for 4 major cities in Europe ➢ Reductions in the pollution level (using NO2 as a proxy) have been observed at the end of March 2020 (20-50% for Paris; 30-70% for Milan region; 30-60% for Madrid; 40-60% for the last week for Athens), as compared to the same period in 2019 PARIS 2019 15-31 March averages MILAN MADRID ATHENS 2020 15-31 March averages
  21. 21. 21 SPASCIA Project objectivesContact Thank you for your attention SPASCIA contact: pascal.prunet@spascia.fr Tel : +33 (0)6 75 55 10 01; +33 (0)5 34 32 03 91 SPASCIA – Parc Technologique du canal – 10 Avenue de l’Europe 31520 Ramonville – France

×