Measurements of nitrogen dioxide total column amounts using a Brewer double spectrophotometer in direct Sun mode

Abstract

[1] NO 2 column amounts were measured for the past 2 years at Goddard Space Flight Center, Greenbelt, Maryland, using a Brewer spectrometer in direct Sun mode. A new ''bootstrap'' method to calibrate the instrument is introduced and described. This technique selects the cleanest days from the database to obtain the solar reference spectrum. The main advantage for direct Sun measurements is that the conversion uncertainty from slant column to vertical column is negligible compared to the standard scattered light observations where it is typically on the order of 100% (2s) at polluted sites. The total 2s errors of the direct Sun retrieved column amounts decrease with solar zenith angle and are estimated at 0.2 to 0.6 Dobson units (DU, 1 DU % 2.7 Â 10 16 molecules cm À2 ), which is more accurate than scattered light measurements for high NO 2 amounts. Measured NO 2 column amounts, ranging from 0 to 3 DU with a mean of 0.7 DU, show a pronounced daily course and a strong variability from day to day. The NO 2 concentration typically increases from sunrise to noon. In the afternoon it decreases in summer and stays constant in winter. As expected from the anthropogenic nature of its source, NO 2 amounts on weekends are significantly reduced. The measurements were compared to satellite retrievals from Scanning Image Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Satellite data give the same average NO 2 column and show a seasonal cycle that is similar to the ground data in the afternoon. We show that NO 2 must be considered when retrieving aerosol absorption properties, especially for situations with low aerosol optical depth.Citation: Cede, A., J. Herman, A. Richter, N. Krotkov, and J. Burrows (2006), Measurements of nitrogen dioxide total column amounts using a Brewer double spectrophotometer in direct Sun mode,

Estimation of the mass absorption cross section of the organic carbon component of aerosols in the Mexico City Metropolitan Area

“…Without further analysis of the T2 data, beyond the scope of this paper, we cannot be certain that this behavior is caused by the same factors acting at the Mexico City site, such as aerosol composition and size distribution. Table 1 for the five case studies considered here, and these values fall into a range of 1 to 3 DU that is consonant with other NO 2 retrievals in areas of moderate pollution (Cede et al, 2006;Heue et al, 2005;Beirle et al, 2004). Using our columnar values of NO 2 and SO 2 we corrected the raw τ ext,λ values obtained from the MFRSR and the SR, and unless otherwise noted, the symbol τ ext,λ indicates corrected values.…”

The use of NO<sub>2</sub> absorption cross section temperature sensitivity to derive NO<sub>2</sub> profile temperature and stratospheric–tropospheric column partitioning from visible direct-sun DOAS measurements

“…Direct-sun/direct-moon (DS/DM) DOAS is equally sensitive to the stratospheric and tropospheric absorbers at SZA < 80 • , and allows for very simple data interpretation (Cede et al, 2006;Herman et al, 2009;Wang et al, 2010;Spinei et al, 2010). This is due to the almost geometric calculation of DS/DM air mass factors (AMFs).…”

“…This is due to the almost geometric calculation of DS/DM air mass factors (AMFs). Compared to MAX-DOAS, it has a lower overall absorption sensitivity (Brewer et al, 1973;Cede et al, 2006) because of shorter path length in the atmosphere.…”

“…The Beer-Lambert law written for a single absorber, NO 2 , with linear temperature-dependent σ (T ) and ideal groundbased DOAS measurements of solar monochromatic light is described according to Eq. (2): ln by an AMF and is defined by solar zenith angle, Earth's surface curvature, and, to a smaller degree, NO 2 profile (at SZA > 80 • ; Cede et al, 2006). Reference spectra are typically measured at the observation conditions with minimum photon path and NO 2 total column.…”

Tropospheric nitrogen dioxide column retrieval from ground-based zenith–sky DOAS observations

“…As cloud cover was substantial during the CINDI campaign, the acquired DS-DOAS data set is relatively scarce. The fundamentals of DS-DOAS are extensively discussed in Brewer et al (1973), Cede et al (2006), and Herman et al (2009).…”