Estimating surface NO2 and SO2 mixing ratios from fast-response total column observations and potential application to geostationary missions

Abstract

Total-column nitrogen dioxide (NO2) data collected by a ground-based sun-tracking spectrometer system (Pandora) and an photolytic-converter-based in-situ instrument collocated at NASA’s Langley Research Center in Hampton, Virginia were analyzed to study the relationship between total-column and surface NO2 measurements. The measurements span more than a year and cover all seasons. Surface mixing ratios are estimated via application of a planetary boundary-layer (PBL) height correction factor. This PBL correction factor effectively corrects for boundary-layer variability throughout the day, and accounts for up to ≈75 % of the variability between the NO2 data sets. Previous studies have made monthly and seasonal comparisons of column/surface data, which has shown generally good agreement over these long average times. In the current analysis comparisons of column densities averaged over 90 s and 1 h are made. Applicability of this technique to sulfur dioxide (SO2) is briefly explored. The SO2 correlation is improved by excluding conditions where surface levels are considered background. The analysis is extended to data from the July 2011 DISCOVER-AQ mission over the greater Baltimore, MD area to examine the method’s performance in more-polluted urban conditions where NO2 concentrations are typically much higher.

The Dawn of Geostationary Air Quality Monitoring: Case Studies From Seoul and Los Angeles

“…These measurements are total NO 2 column with no differentiation of stratospheric or tropospheric NO 2 contributions, but as discussed in section GeoTASO, stratospheric contributions are relatively small and uniform over the SMA and the LA Basin. Data from these instruments have been used to assess spaceand aircraft-based retrievals of NO 2 columns (Flynn et al, 2014;Nowlan et al, 2016;Goldberg et al, 2017), as well as to study the spatiotemporal variability of trace gases in urban environments (Tzortziou et al, 2015) and column-to-surface relationships and their relation to boundary layer depth (Flynn et al, 2014;Knepp et al, 2015). Further understanding the effects of boundary layer depth on air quality has been identified as a "most important" objective by the National Academy of Sciences' most recent Decadal Survey (2017-2027) (National Academies of Sciences Engineering Medicine, 2018).…”

Evaluation of OMI operational standard NO<sub>2</sub> column retrievals using in situ and surface-based NO<sub>2</sub> observations

“…The CAPABLE site is located in a coastal suburban area, which could experience sporadic local and transported NO x emissions. Additional details on the CAPABLE site can be found in Knepp et al (2013). These measurements are useful to examine spatial and temporal variation in the OMI retrievals.…”

Estimation of Surface NO2 Volume Mixing Ratio in Four Metropolitan Cities in Korea Using Multiple Regression Models with OMI and AIRS Data

“…This NO 2 fraction in upper tropospheric might cause either small or negligible reduction in correlations of the OMI NO 2 VCD between and surface NO 2 VMR as the upper part of the troposphere (free troposphere) contribution is assumed to be negligible [28]. To reflect the BLH in the regression equation, Trop NO 2 VCD OMI is first divided by BLH AIRS to calculate the NO 2 concentration in the PBL and then converted to the NO 2 mixing ratio in the PBL (BLH NO 2 VMR OMI ) using Temp AIRS and Press AIRS [29] as shown Table 2. Only a single OMI pixel contained completely within an AIRS pixel was used.…”

“…PressAIRS [29] as shown Table 2. Only a single OMI pixel contained completely within an AIRS pixel was used.…”