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Initial results on OMI NO 2 Validation during CINDI

Initial results on OMI NO 2 Validation during CINDI. A contribution to the BIRA Cindi Workshop Yipin Zhou , Dominik Brunner, and Brigitte Buchmann Empa, Swiss Federal Laboratories for Materials Testing and Research Dübendorf, Switzerland. With special thanks to Florence Goutail

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Initial results on OMI NO 2 Validation during CINDI

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  1. Initial results on OMI NO2 Validation during CINDI A contribution to the BIRA Cindi Workshop Yipin Zhou, Dominik Brunner, and Brigitte Buchmann Empa, Swiss Federal Laboratories for Materials Testing and Research Dübendorf, Switzerland With special thanks to Florence Goutail Folkert Boersma Katrijn Clemer BIRA

  2. Outlook • Comparison of SAOZ NO2 column with In-situ column calculated with Lidar and Ceilometer boundary height. • Introduction to Empa OMI NO2 retrieval. • Comparison of OMI NO2 column with SAOZ.

  3. In-situ vs SAOZ NO2 columns (10 mins resolution) LIDAR PBL tops June 24th 11 < UTC < 18

  4. In-situ vs SAOZ NO2 columns (10 mins resolution) Ceilometer PBL tops 11 < UTC < 18

  5. In-situ vs SAOZ NO2 columns (1 hour averages) 11 < UTC < 18

  6. OMI tropospheric NO2 retrieval • Based on DOMINO retrieval (TM4 a-priori, SCD, cloud algorithm) • Improved AMF calculation (high spatial resolution terrain height, considering BRDF effect based on high spatial and temporal resolution MODIS data set) • On-line calculation with LIDORT 3.3

  7. SZA OMI tropospheric NO2 retrieval Surface reflectance generally depends on solar zenith angle (SZA) and viewing zenith angle (VZA) volumetric geometric fvol in November fvol in July

  8. VZA OMI tropospheric NO2 retrieval Example in summer (July) BRF BRF Typical OMI swath Relative error in NO2

  9. OMI tropospheric NO2 retrieval Mean NO2 VTCs averaged over the years 2006 and 2007 (July, Nov)

  10. OMI pixel selection For each orbit (VZA <65), find the pixel closest to the Cabauw tower. Average if there are two pixels with similiar distance.

  11. OMI vs SAOZ Row anomaly (28th-40th,46th-50th,53th-54th pixels are affected ) Empa retrieval (screening, cloud fraction < 25%)

  12. OMI vs SAOZ n=12 (only good pixels) Cloud radiance fraction (cloud fraction < 25%) n=20 (including row anomaly pixels)

  13. OMI vs SAOZ Cloud screening is necessary for validation

  14. Conclusions • NO2 columns constructed from the in-situ measurement agrees well with the SAOZ columns. Better agreement is found from the in-situ columns calculated with boundary height from Lidar and SAOZ retrieved with IASB AMFs calculated using their NO2 and aerosol profiles . • For the pixels with cloud fraction smaller than 25%, the correlation of the OMI NO2 columns and the SAOZ columns are better than 0.6. Empa retrieval shows good agreement even when the sample size is quite small. Albedo effect is not obvious during this time period. • Cloud shows larger impact on the NO2 retrieval than the row anomaly.

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