Abstract
Abstract. This work presents a new high-resolution NO2 dataset derived from the NASA Ozone Monitoring Instrument (OMI) NO2 version 3.0 retrieval that can be used to estimate surface-level concentrations. The standard NASA product uses NO2 vertical profile shape factors from a 1.25° × 1° (∼ 110 km × 110 km) resolution Global Model Initiative (GMI) model simulation to calculate air mass factors, a critical value used to determine observed tropospheric NO2 vertical columns. To better estimate vertical profile shape factors, we use a high-resolution (1.33 km × 1.33 km) Community Multi-scale Air Quality (CMAQ) model simulation constrained by in situ aircraft observations to recalculate tropospheric air mass factors and tropospheric NO2 vertical columns during summertime in the eastern US. In this new product, OMI NO2 tropospheric columns increase by up to 160 % in city centers and decrease by 20–50 % in the rural areas outside of urban areas when compared to the operational NASA product. Our new product shows much better agreement with the Pandora NO2 and Airborne Compact Atmospheric Mapper (ACAM) NO2 spectrometer measurements acquired during the DISCOVER-AQ Maryland field campaign. Furthermore, the correlation between our satellite product and EPA NO2 monitors in urban areas has improved dramatically: r2 = 0.60 in the new product vs. r2 = 0.39 in the operational product, signifying that this new product is a better indicator of surface concentrations than the operational product. Our work emphasizes the need to use both high-resolution and high-fidelity models in order to recalculate satellite data in areas with large spatial heterogeneities in NOx emissions. Although the current work is focused on the eastern US, the methodology developed in this work can be applied to other world regions to produce high-quality region-specific NO2 satellite retrievals.
Highlights
Tropospheric NO2 is a trace gas toxic to human health and during ideal atmospheric conditions can photolyze to create O3, another toxic air pollutant with a longer atmospheric lifetime
We evaluate our new product by comparing to DISCOVER-AQ observations
This study demonstrates the critical importance of using high-resolution a priori NO2 shape factors to develop air mass factor (AMF) in and around metropolitan areas
Summary
Tropospheric NO2 is a trace gas toxic to human health and during ideal atmospheric conditions can photolyze to create O3, another toxic air pollutant with a longer atmospheric lifetime. HNO3 can react with ammonia to create nitrate aerosols, which contribute to haze and are harmful to human health. There are some natural sources of nitrogen oxides (NOx ≡ NO + NO2), such as from soil through microbial nitrification and denitrification (Conrad, 1996), lightning (Ridley et al, 1996), and natural wildfires (Val Martin et al, 2006), but the majority of the NO2 in our atmosphere today originates from. The NO and NO2 species are often grouped into a single species called NOx. In the presence of hydroperoxy (HO2) or organic peroxy radicals (RO2, where R is any organic group), NO can be oxidized to NO2 without consuming ozone. In the presence of hydroperoxy (HO2) or organic peroxy radicals (RO2, where R is any organic group), NO can be oxidized to NO2 without consuming ozone This is the rate-limiting step in the chemical chain reaction producing tropospheric ozone
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