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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 Mar 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Improved aerosol correction for OMI tropospheric NO2 retrieval over East Asia: constraint from CALIOP aerosol vertical profile
Mengyao Liu1,2, Jintai Lin1, K. Folkert Boersma2,3, Gaia Pinardi4, Yang Wang5, Julien Chimot6, Thomas Wagner5, Pinhua Xie7,8,9, Henk Eskes2, Michel Van Roozendael4, Fran├žois Hendrick4, Pucai Wang10, and Yingying Yan1 1Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
2Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
3Meteorology and Air Quality department, Wageningen University, Wageningen, the Netherlands
4Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
5Max Planck Institute for Chemistry, Mainz, Germany
6Department of Geoscience and Remote Sensing (GRS), Civil Engineering and Geosciences, TU Delft, the Netherlands
7Anhui Institute of Optics and Fine Mechanics, Key laboratory of Environmental Optics and Technology, Chinese Academy of Sciences, Hefei, China
8CAS Center for Excellence in Urban Atmosphe ric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
9School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei, China
10IAP/CAS, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Abstract. Satellite retrieval of vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO2) is critical for NOx pollution and impact evaluation. For regions with high aerosol loadings, the retrieval accuracy is greatly affected by whether aerosol optical effects are treated implicitly (as additional effective clouds) or explicitly, among other factors. Our previous POMINO algorithm explicitly accounts for aerosol effects to improve the retrieval especially in polluted situations over China, by using aerosol information from GEOS-Chem simulations with further monthly constraint by MODIS/Aqua AOD data. This study updates the retrieval algorithm to POMINO v1.1, by constructing a monthly climatological dataset of aerosol extinction profiles, based on Level-2 CALIOP/CALIPSO data over 2007–2015, to better constrain the modeled aerosol profiles.

We find that GEOS-Chem captures the month-to-month variation of CALIOP aerosol layer height but with a systematic underestimate by about 300–600 m (season and location dependent), due to a too strong vertical gradient of extinction above 1 km. Correcting the model aerosol extinction profiles results in small changes in retrieved cloud fraction, increases in cloud top pressure (within 2–6 % in most cases), and increases in tropospheric NO2 VCD by 4–16 % over China on a monthly basis in 2012. The improved NO2 VCDs (in POMINO v1.1) are more consistent with independent ground-based MAX-DOAS observations (R2 = 0.80, NMB = −3.4 %) than POMINO (R2 = 0.80, NMB = −9.6 %) and DOMINO v2 (R2 = 0.68, NMB = −2.1 %) are. Especially on haze days, R2 reaches 0.76 for POMINO v1.1, much higher than that for POMINO (0.68) and DOMINO v2 (0.38). Furthermore, the increase in cloud pressure likely reveals a more realistic vertical relationship between cloud and aerosol layers, with aerosols situated above the clouds in certain months instead of always below the clouds. Our POMINO v1.1 algorithm will be applied to the recently launched TropOMI sensor.

Citation: Liu, M., Lin, J., Boersma, K. F., Pinardi, G., Wang, Y., Chimot, J., Wagner, T., Xie, P., Eskes, H., Van Roozendael, M., Hendrick, F., Wang, P., and Yan, Y.: Improved aerosol correction for OMI tropospheric NO2 retrieval over East Asia: constraint from CALIOP aerosol vertical profile, Atmos. Meas. Tech. Discuss.,, in review, 2018.
Mengyao Liu et al.
Mengyao Liu et al.
Mengyao Liu et al.


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Publications Copernicus
Short summary
China has become the world's largest emitting country of NOx, which mainly come from vehicle exhausts, power plants, etc. However, there is no official ground-based measurements before 2013, so satellite have been widely used to monitor and analyze NOx pollution here. Aerosol is the key factor to influence the accuracy of the satellite NOx product. Our study provide a more accurate way to account aerosol's influence comparing to current wildly used products.
China has become the world's largest emitting country of NOx, which mainly come from vehicle...