Validation of the Ozone Monitoring Instrument Total Ozone Column and Implications for Trend Studies M. Kroon 1, R.D. McPeters 2, J.P. Veefkind 1, G. Labow 2, D. Balis 3, I. Petropavlovskikh 4, P.K. Bhartia 2, R. Shetter 4 and P.F. Levelt 1 1.Royal Netherlands Meteorological Institute, 2.NASA Goddard Space Flight Center, 3.Aristotle University of Thessaloniki, 4.NOAA/ESRL, 5.National Center for Atmospheric Research OMI Science Team Meeting Helsinki, 24 June 2008

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 2 Total Ozone Column ECS2 > COL3 OMI TOMS V8.5 [DU]OMI TOMS V8.0 [DU] ECS2COL3September 2005

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 3 Total Ozone Column ECS2 > COL3 ECS2COL3 DOAS v1.0.5 [DU]DOAS v1.0.1 [DU] September 2005

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 4 Changing Collection OMI-DOAS OMDOAO3 algorithm v1.0.5 release for OMI Collection 3 data. Collection 3 Level 1B has better dark current and stray light corrections yielding better fitting residuals and lower chi-squared. Treatment of high reflective surfaces (snow/ice) changed. Effective cloud fraction set to zero and surface albedo fitted (~OMTO3). Airmass factor tables updated. AMF tables primary cause for Solar Zenith Angle dependent bias. New air mass factor tables are based on improved radiative transfer calculations. Look-up table for cloud radiance fraction updated. New radiative transfer calculations include atmospheric sphericity. New static irradiance file produced by combining Solar irradiance data of collection 3 for year 2005.

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 5 Changing Collection OMI-TOMS OMTO3 algorithm v8.5 release for OMI Collection 3 data. Ingesting daily OMCLDRR (Raman) cloud effective pressure and fraction “CloudFractionForO3” and “CloudPressureForO3”. Treatment of high reflective surfaces (snow/ice) changed. Cloud fraction set to zero at snow ice fraction >50%. Jump at Solar Zenith Angle 69º corrected by switching off change in climatological ozone profile used. Collection 3 Level 1B stray light corrections change yields OMTO3 to drop 6-7 DU on global scale. Under discussion!. OMSO2 algorithm improved yielding higher SO2 PBL values hence more SO2 polluted pixels correctly flagged hence less influence.

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 6 Total Ozone Column ECS2 > COL3 Closer Match! Close Match

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 7 Total Ozone Column ECS2 > COL < Regression < < Correlation < < Regression < < Correlation < 0.98

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 8 Total Ozone Column ECS2 > COL3 -7 < Difference < 1 8 < Deviation < < Difference < 3 10 < Deviation < 19

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 9 Total Ozone Column ECS2 > COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 10 TO3C Difference ECS2 > COL3 OMI TOMS V8.5 - DOAS v1.0.5 [DU] October 2005 OMI TOMS V8.0 - DOAS v1.0.1 [DU] ECS2COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 11 TO3C Single Orbits ECS2

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 12 TO3C Single Orbits COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 13 Influence of Sulphur Dioxide ECS N E E 12.4 N 20.2 N E E 12.4 N

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 14 Influence of Sulphur Dioxide COL N E E 12.4 N 20.2 N E E 12.4 N

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 15 Influence of Clouds ECS2

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 16 Influence of Clouds COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 17 Ground Based vs OMTO3 OMI AO Validation of OMI total ozone using ground-based Brewer observations. Dr. Dimitris Balis, Aristotle University of Thessaloniki - Laboratory of Atmospheric Physics, Greece ECS2COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 18 Ground Based vs OMTO3 OMI AO Validation of OMI total ozone using ground-based Brewer observations. Dr. Dimitris Balis, Aristotle University of Thessaloniki - Laboratory of Atmospheric Physics, Greece ECS2COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 19 Ground Based vs OMDOAO3 OMI AO Validation of OMI total ozone using ground-based Brewer observations. Dr. Dimitris Balis, Aristotle University of Thessaloniki - Laboratory of Atmospheric Physics, Greece ECS2COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 20 Ground Based vs OMDOAO3 OMI AO Validation of OMI total ozone using ground-based Brewer observations. Dr. Dimitris Balis, Aristotle University of Thessaloniki - Laboratory of Atmospheric Physics, Greece ECS2COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 21 BrewerDobson /G  (O-G) /G  (O-G) OMI DOAS0.483 %2.754 %0.070 %1.653 % OMI DOAS* %0.200 %0.086 %1.601 % OMI TOMS %2.704 % %1.032 % OMI TOMS* %0.425 % %1.064 % * No South Pole (lat > 75 S) Ground Based Validation COL3

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 22 NASA WB-57 no.926NASA DC-8 no.817

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 23 DOAS vs CAFS ∆=10 DU=2.9% TOMS vs CAFS ∆= -5.8 DU=-1.8% Polar-AVE OMI Orbit 2890 CAFS

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 24 Aura Validation Experiment OMI CAFS OMI-DOASOMI-TOMS OMI-CAFS(O-C)/OSTDOMI-CAFS(O-C)/OSTD Polar-AVE10.12 DU2.89 %10.36 DU-5.85 DU-1.75 %12.54 DU Houston AVE-6.06 DU2.09 %9.09 DU-2.27 DU-0.77 %9.47 DU Costa Rica AVE-8.12 DU-3.40 %5.92 DU-8.61 DU-3.62 %3.89 DU ALL AVE-2.02 DU-0.70 %11.70 DU-5.14 DU %9.59 DU

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 25 Solar Zenith Angle NH SH WG COL3 ECS2

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 26 Required Accuracy 3% 100 DU Validation of ECS2 has led to many modifications made to the respective algorithms for COL3 reprocessing. For COL3 agreement is found within 1-2 % with reference data. Continuing the TOMS total ozone record (> November 1978) is thus achievable with OMI total ozone. Remaining difference between OMI- TOMS and OMI-DOAS total ozone estimates are significant in size compared to dynamic range covered by trends. Both algorithms are sensitive to calibration changes, but not up to the level that becomes significant for trends.

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 27 Data Availability OMI DOAS Total Ozone Column : NASA DISC and NASA AVDC OMI TOMS Total Ozone Column : NASA DISC and NASA AVDC OMI Near Real Time Total Ozone Column : KNMI TEMIS (NRT) (Assim) OMI Very Fast Delivery Total Ozone Column : FMI OMIVFD OMI Ozone Profiles : NASA AVDC (provisional)

Dr. Mark Kroon – KNMI - OSTM13 – FinlandSlide 28