Abstract
Abstract. We describe the new version 3.0 NASA Ozone Monitoring Instrument (OMI) standard nitrogen dioxide (NO2) products (SPv3). The products and documentation are publicly available from the NASA Goddard Earth Sciences Data and Information Services Center (https://disc.gsfc.nasa.gov/datasets/OMNO2_V003/summary/). The major improvements include (1) a new spectral fitting algorithm for NO2 slant column density (SCD) retrieval and (2) higher-resolution (1° latitude and 1.25° longitude) a priori NO2 and temperature profiles from the Global Modeling Initiative (GMI) chemistry–transport model with yearly varying emissions to calculate air mass factors (AMFs) required to convert SCDs into vertical column densities (VCDs). The new SCDs are systematically lower (by ∼ 10–40 %) than previous, version 2, estimates. Most of this reduction in SCDs is propagated into stratospheric VCDs. Tropospheric NO2 VCDs are also reduced over polluted areas, especially over western Europe, the eastern US, and eastern China. Initial evaluation over unpolluted areas shows that the new SPv3 products agree better with independent satellite- and ground-based Fourier transform infrared (FTIR) measurements. However, further evaluation of tropospheric VCDs is needed over polluted areas, where the increased spatial resolution and more refined AMF estimates may lead to better characterization of pollution hot spots.
Highlights
Emissions and concentrations of nitrogen oxides (NOx = NO + NO2) are regulated in several countries, as nitrogen dioxide (NO2) is a toxic pollutant (US EPA, 2017) and NOx leads to the formation of surface-level ozone, acid rain, and particular matter (Seinfeld and Pandis, 1998)
This paper describes the new Ozone Monitoring Instrument (OMI) operational NO2 standard product, version 3 (SPv3), which is available from the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC: https://disc.gsfc.nasa.gov/datasets/ OMNO2_V003/summary/)
While the revised slant column density (SCD) estimates come from a new retrieval algorithm, the air mass factors (AMFs) refinements relate to updates in the Global Modeling Initiative (GMI) chemical and transport model inputs, primarily emission inventories and a horizontal resolution that is twice as fine in both latitude and longitude
Summary
The previous NASA algorithm (version SPv2) used the same NO2 SCDs as DOMINO v2 (Boersma et al, 2011), employing different approaches to the stratosphere–troposphere separation (STS) and AMF calculation (Bucsela et al, 2013) Both products were in general agreement and produced similar regional trends in tropospheric VCDs (Krotkov et al, 2016), but comparison of OMI stratospheric NO2 VCDs (SPv2 and DOMINO v2) with other independent measurements revealed that they were overestimated by as much as 40 % over unpolluted regions (Belmonte Rivas et al, 2014).
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