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BErkeley High Resolution (BEHR) OMI NO2 Prototype High Temporal Resolution Product

Citation

Laughner, Joshua (2016), BErkeley High Resolution (BEHR) OMI NO2 Prototype High Temporal Resolution Product, Other, https://doi.org/10.6078/D1KS3M

Abstract

The BErkeley High Resolution (BEHR) OMI NO2 Prototype High Temporal Resolution Product makes use of high spatial and temporal resolution a priori NO2 profiles for a limited domain in the southeast United States, covering 1 June-30 Aug 2013. These retrievals have been used to evaluate the impact of daily temporal resolution of the high-spatial-resolution a priori NO2 profiles needed for the retrieval

Methods

Tropospheric slant columns are obtained from the NASA OMI Standard Product v2.1 (SP2). Tropospheric air mass factors (AMFs) are computed using the scattering weights from the SP2 look up table and a priori NO2 profiles simulated with WRF-Chem at 12 km spatial resolution. Inputs to the scattering weight look up table are the sun-satellite geometry, surface albedo from the MODIS combined black-sky albedo product (MCD43C3) and the terrain heights from the Global Land One-km Base Elevation (GLOBE) project database (https://www.ngdc.noaa.gov/mgg/topo/globe.html). The AMF for each pixel is the average of clear and cloudy AMFs; weighted by the cloud radiance fraction for that pixel. Cloudy AMFs use the OMI O2-O2 cloud pressure as the surface pressure and 0.8 as the cloud albedo. These AMFs are used to compute the BEHR tropospheric vertical column densities (VCDs).

Usage Notes

There are nine .zip archives containing retrievals for the period 1 June-30 Aug 2013. The three .zip files marked "pseudo" contain pseudo-retrievals for this period; these retrievals use the same set of OMI pixels for all days. Thus, VCDs are not included in these files, only the BEHR AMFs. The purpose is to show the impact of daily vs. NO2 profiles on the AMFs. The three pseudo-retrieval zip archives differ only in the NO2 profiles used: daily profiles, monthly average profiles, or hybrid profiles, which use daily profiles below 750 hPa and monthly average above. The other six .zip archives (marked "prototype") contain full retrievals with the actual pixels for each day. Again, three different sets of NO2 a priori profiles are used, daily, monthly average, and coarse monthly average profiles (simulated at 108 km spatial resolution). The "native" files contain data at the native OMI pixel resolution; the "gridded" files contain this data oversampled to a 0.05x0.05 degree grid. The latter is easier to average over time, since the geographic coordinates of each grid cell is fixed from day to day. This data should be filtered for quality by the vcdQualityFlags and XTrackQualityFlags fields. Only pixels where vcdQualityFlags is an even integer and XTrackFlags is 0 should be used. Cloud filtering is also recommended for most applications; we require that CloudFraction is less than or equal to 0.2. Although the full prototype retrievals contain pixels throughout the continental US, only pixels within the approximate domain 89 to 79 deg. W and 30 to 38 deg. N have valid data.

Funding

National Aeronautics and Space Administration, Award: NNX14AK89H

National Aeronautics and Space Administration, Award: NNX15AE37G

National Aeronautics and Space Administration, Award: NNX14AH04G

Smithsonian Institution, Award: SV3-83019