Abstract
Abstract. We describe upgrades to the Berkeley High Resolution (BEHR) NO2 satellite retrieval product. BEHR v3.0B builds on the NASA version 3 standard Ozone Monitoring Instrument (OMI) tropospheric NO2 product to provide a high spatial resolution product for a domain covering the continental United States and lower Canada that is consistent with daily variations in the 12 km a priori NO2 profiles. Other improvements to the BEHR v3.0 product include surface reflectance and elevation, and factors affecting the NO2 a priori profiles such as lightning and anthropogenic emissions.We describe the retrieval algorithm in detail and evaluate the impact of changes to the algorithm between v2.1C and v3.0B on the retrieved NO2 vertical column densities (VCDs). Not surprisingly, we find that, on average, the changes to the a priori NO2 profiles and the update to the new NASA slant column densities have the greatest impact on the retrieved VCDs. More significantly, we find that using daily a priori profiles results in greater average VCDs than using monthly profiles in regions and times with significant lightning activity.The BEHR product is available as four subproducts on the University of California DASH repository, using monthly a priori profiles at native OMI pixel resolution (https://doi.org/10.6078/D1N086) and regridded to 0.05° × 0.05° (https://doi.org/10.6078/D1RQ3G) and using daily a priori profiles at native OMI (https://doi.org/10.6078/D1WH41) and regridded (https://doi.org/10.6078/D12D5X) resolutions. The subproducts using monthly profiles are currently available from January 2005 to July 2017, and will be expanded to more recent years. The subproducts using daily profiles are currently available for years 2005–2010 and 2012–2014; 2011 and 2015 on will be added as the necessary input data are simulated for those years.
Highlights
Nitrogen oxides (NO + NO2 ≡ NOx) are trace gases in the atmosphere and are key species controlling air quality and affecting radiative balance
We describe each change in detail and examine the effect of each individual change on the calculated vertical column densities (VCDs). v3.0A was available on the Berkeley High Resolution (BEHR) website between November 2017 and July 2018; v3.0B replaced v3.0A on the website and the static repositories (Laughner et al, 2018a, b, c, d) in July 2018
We focus on the 2012 data as an example to understand the effect each change to the algorithm has on the final VCDs
Summary
Nitrogen oxides (NO + NO2 ≡ NOx) are trace gases in the atmosphere and are key species controlling air quality and affecting radiative balance. Aerosol effects are often assumed to be implicitly accounted for in cloud properties (e.g., Boersma et al, 2011), but have been treated explicitly by some products (e.g., Lin et al, 2015) The accuracy of these input data has a significant impact on the accuracy of the AMFs and the vertical columns. The Berkeley High Resolution (BEHR) Ozone Monitoring Instrument (OMI) NO2 retrieval is one such regional product that provides tropospheric NO2 VCDs over part of North America (approximately 125 to 65◦ W, 25 to 50◦ N) using high-resolution a priori inputs. Surface pressure calculation was changed to follow Zhou et al (2009) using GLOBE terrain elevation and WRF surface pressure These changes all affect the tropospheric VCDs. BEHR provides a “visible-only” VCD, that is, the VCD excluding NO2 below clouds for users interested in, e.g., cloud slicing methods (Choi et al, 2014). We focus on the 2012 data as an example to understand the effect each change to the algorithm has on the final VCDs
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