1. S5P tropospheric ozone product: Convective Cloud Differential method First German S5P Verification Meeting Bremen, 28 - 29 November 2013 Pieter Valks DLR, Remote Sensing Technology Institute (IMF)

2. 2 Outline Convective-Cloud-Differential (CCD) algorithm for S5P Analyses of CCD method with GOME-2 data Analyses of cloud parameters Variability in stratospheric and upper tropospheric ozone Tropical tropospheric ozone column Further analyses and development for S5P

3. 3 S5P tropical tropospheric ozone with CCD method Convective-cloud-differential (CCD) method above cloud and clear-sky ozone column measurements Tropical tropospheric ozone columns (TTOC) below ~200 hPa S5P data required: Total ozone columns Effective cloud fractions, cloud albedo and cloud-top pressures (OCRA and ROCINN)

4. 4 S5P cloud parameters used for CCD method Effective cloud fraction S5P_CLOUD_OCRA f > 0.8 (stratospheric column) f < 0.1 (cloud free) Cloud pressure and albedo S5P_CLOUD_ROCINN CTP < 300 hPa CTA > 0.8 (deep convective clouds)

5. 5 Stratospheric ozone column calculation Above-cloud ozone column (ACOC) using S5P Level-2 total ozone product Selection of S5P measurements in the tropics (20°N-20°S): Deep convective tropical clouds (f > 0.8, CTP 0.8) Low ozone concentrations inside cloud East Indian Ocean / Western Pacific (70°E – 170°W) V ac = SCD / AMF cloud (no ghost column) Stratospheric ozone column (monthly mean) 1.25° latitude bands Stratospheric ozone column independent of longitude

6. 6 Tropical tropospheric ozone column Tropical Tropospheric Ozone Column (TTOC) S5P Level-3 product Selection of cloud-free S5P L2 ozone measurements (f < 0.1) V clear = SCD / AMF clear Monthly (weekly) mean values on a 1.25° by 2.5° lat-lon grid (20°N-20°S) GOME-2 Tropospheric O 3 Oct. 2010

7. 7 Analyses of CCD method with GOME-2 data  Analyses of cloud parameters  Variability in stratospheric and upper tropospheric ozone  Tropical tropospheric ozone column  Exemplary results  Comparison with ozonesonde measurements

8. 8 Cloud parameters (OCRA/ROCINN) Frequency of deep convective clouds (f > 0.8, CTP 0.8)

9. 9 Cloud parameters (OCRA/ROCINN) Frequency of deep convective clouds (f > 0.8, CTP 0.8)

10. 10 Cloud parameters (OCRA/ROCINN) Histogram of cloud pressure and albedo for Eastern Indian Ocean / Western Pacific (12.5°S - 12.5°N, 70°E – 170°W, f > 0.8) Cloud Pressure Jan. 2008Cloud Albedo Jan. 2008

11. 11 Cloud parameters (OCRA/ROCINN) Histogram of cloud pressure and albedo for Eastern Indian Ocean / Western Pacific (12.5°S - 12.5°N, 70°E – 170°W, f > 0.8) Cloud Pressure July 2008Cloud Albedo July 2008

12. 12 Variability in stratospheric ozone column Monthly mean stratospheric ozone column 1.25° latitude bands between 20°S - 20°N Assumption: stratospheric ozone column independent of longitude in tropics Comparison of GOME-2 CCD stratospheric ozone column with ozonesondes Comparison for 8 SHADOZ sites Bias: ≤ 3 DU RMS differences: 3-7 DU Comparisons with other stratospheric ozone satellite measurements (Ziemke et al.) TOMS CCD comparison with SAGE II (Bias: 1-4 DU; RMS differences: 4-5 DU) OMI CCD comparison with MLS (Bias: 1-3 DU; RMS differences: 2-3 DU)

13. 13 Variability in upper tropospheric ozone Ozone concentrations in deep convective clouds (cloud slicing technique) Above-cloud O 3 column Indian Ocean 1-3 Oct. 2007 10-20ºN/70-90ºE Above-cloud O 3 column Western Pacific 1-3 Oct. 2007 10-20ºS/160-180ºE Mean ozone mixing ratio: ~7 ppbvMean ozone mixing ratio: 4 ~ppbv

14. 14 Variability in upper tropospheric ozone Ozone concentrations in deep convective clouds (cloud slicing technique) Above-cloud O 3 column Indian Ocean 1-3 March 2008 0-10ºN/70-90ºE Above-cloud O 3 column Western Pacific 1-3 March 2008 0-10ºS/120-140ºE Mean ozone mixing ratio: ~6 ppbvMean ozone mixing ratio: ~8 ppbv

15. 15 GOME-2B tropical tropospheric NO 2 and ozone Tropospheric Ozone Tropospheric NO 2 October, 2013

16. 16 GOME-2 tropical tropospheric NO 2 and ozone Tropospheric Ozone Tropospheric NO 2 September, 2010

17. 17 Comparison with ozonesonde measurements Bias: -0.9 DU RMS: 3.4 DU Natal, Brazil (5ºS, 35ºW) R: 0.89

18. 18 Comparison with ozonesonde measurements Bias: -1.4 DU RMS: 3.9 DU Ascension Island (8ºS, 15ºW) R: 0.85

19. 19 Comparison with ozonesonde measurements Bias: -1.7 DU RMS: 3.6 DU American Samoa (14ºS, 171ºW) R: 0.75

20. 20 GOME-2 tropospheric ozone ENSO index Nino 3.4 ENSO temp. index temperature anomalie in eastern Pacific Ozone ENSO index ozone column difference between western and eastern Pacific R = 0.90 Correlation between Nino 3.4 Temp. ENSO and Ozone ENSO index

21. 21 Further analyses and development for S5P Cloud parameters Same cloud algorithms (OCRA/ROCINN) used for GOME-2 and S5P Cloud selection criteria (f, CTP, CTA) to be optimized for S5P dependent on FOV, ground pixel size, etc. CCD method sensitive to albedo related instrument effects (e.g. TTOC bias between GOME-2A and GOME-2B) Spatial and temporal resolution Temporal resolution: monthly, weekly, daily? Valid latitude range varies with month (but only for tropics) Spatial resolution: currently 1.25° x 2.5° lat-lon (GOME-2) Analyse with OMI data and (simulated) S5P data Operational processing and product format Realistic estimates of CPU / RAM / Product size Product format Implementation in PDGS (Level-3 product)