Pomino: An Improved Satellite NO2 Product for the Ozone Monitoring Instrument

Monday, 15 December 2014
Jintai Lin1, Randall Martin2, K. Folkert Boersma3, Maarten Sneep3, Piet Stammes3, Robert J D Spurr4, Pucai Wang5, Michael Van Roozendael6, Katrijn Clemer7 and Hitoshi Irie8, (1)Peking University, Beijing, China, (2)Dalhousie University, Halifax, NS, Canada, (3)Royal Netherlands Meteorological Institute, De Bilt, Netherlands, (4)Rt Solutions Inc, Cambridge, MA, United States, (5)IAP Insititute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (6)Belgian Institute for Space Aeronomy, Brussels, Belgium, (7)Instituut voor sterrenkunde, Heverlee, Belgium, (8)Chiba University, Chiba, Japan
Tropospheric NO2 columns retrieved from satellite instruments are useful to infer NOx pollution, NOx emissions and atmospheric chemistry. Current satellite products are subject to limitations in assumptions of aerosol optical effects, surface reflectance anisotropy, vertical profiles of NO2, and/or cloud optical properties. Here we develop an improved Peking University Ozone Monitoring Instrument NO2 product (POMINO) for China, complementing the popular DONIMO v2 product.

POMINO explicitly accounts for aerosol optical effects, angular dependence of surface reflectance, and dynamically varying atmospheric profiles of air pressure, air temperature and NO2 at a high horizontal resolution (50 km). Prior to the NO2 retrieval, we retrieve cloud top pressure and cloud fraction using consistent assumptions about the states of the atmosphere and surface.

For our NO2 and cloud retrievals, we adopt from KNMI (via www.temis.nl) the SCDs of tropospheric NO2 (DOMINO v2) and O2-O2 dimer (OMCLDO2 v1.1.1.3), the TOA reflectance, and some other ancillary information.

We develop the AMFv6 code for radiative transfer calculation, based on LIDORT v3.6. Radiative transfer is calculated explicitly for each satellite pixel with no need to use a look-up table. The calculation of AMFv6 is parallelized and is sufficiently fast so that one day of retrieval with global coverage would only take about three hours using 16 CPU cores.

POMINO is consistent with MAX-DOAS NO2 data in China, with a R2of 0.96 as compared to the value at 0.72 for DOMINO v2. The improved consistency is related to explicit pixel-by-pixel radiative transfer calculation (instead of using a look-up table), consistent treatments of all parameters in retrieving clouds and NO2, explicit consideration of aerosol optical effects (rather than adjusting ‘effective’ clouds to implicitly account for aerosols), and consideration of surface reflectance anisotropy. Additional analyses are being conducted on the daily, seasonal and interannual variability of NO2 revealed by the POMINO data, as well as impacts on the study of NOx chemistry and emissions.

Our AMFv6 code is available for public use. More information can be found at http://www.atmos.pku.edu.cn/acm/satellite_no2.html.