Temperature dependent NO₂ cross sections at high spectral resolution

Abstract

Abstract. The importance of nitrogen dioxide in both the troposphere and the stratosphere has been known for some years, and since the early 1970s, spectroscopic determinations have played an important role in understanding NOx chemistry. Spectroscopic measurements of the atmosphere have improved in quality in recent years to the point that an accurate determination of the NO 2 absorption cross section is essential to accurate retrievals of not only NO 2 but also less abundant species in the troposphere and stratosphere. NO2 is such a large absorber (approximately 1% at large air mass) in the stratosphere at twilight or in the troposphere under even mildly polluted conditions, that if it is not properly removed from observed spectra, the spectra of the more subtle species are masked and cannot be measured at all. We present cross sections of NO2 in the spectral region 350-585 nm at four temperatures between 217 and 298 K and total pressures between 100 and 600 torr at a mixing ratio of 84.1 ppmv and at a spectral resolution sufficient for accurate convolution with instruments typically used to measure atmospheric NO 2. Data will be presented to demonstrate the presence of NO 2 pressure dependence in high resolution. A detailed comparison with commonly used literature cross sections is made to show how such instrument parameters as wavelength accuracy, resolution, spectrograph scattered light, and data sampling affect the usefulness of the observed cross section.

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

“…At these low residual levels, zenith sky and MAX-DOAS measurements indeed reveal NO 2 temperature sensitivity. This encouraged high-quality laboratory measurements of NO 2 cross sections in the UV and visible parts of spectrum at different temperatures from 220 K to room temperatures (Harder et al, 1997;Vandaele et al, 1998). However, these laboratory NO 2 absorption cross sections at 220 K and room temperature show high cross correlation.…”

Cavity Ring-Down and Cavity-Enhanced Detection Techniques for the Measurement of Aerosol Extinction

“…In the green spectral region at 532 nm, significant gaseous extinction is due to scattering by air (13.9 Mm −1 at STP; Anderson et al 1996) and absorption by nitrogen dioxide (0.402 Mm −1 /(ppb NO 2 ) at STP; Harder et al 1997;Arnott et al 2000) and ozone (0.0076 Mm −1 /(ppb O 3 ) at STP; Brion et al 1998). Particle and gaseous contributions can be distinguished by the use of either a particle filter or a gas denuder in the sample stream.…”

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

“…The spectral range for IO retrieval is extended to [416 nm, 465 Bösch et al (2003)) covering six strong (5←0, 4←0, 3←0, 2←0, 1←0, 0←0) vibrational bands of the IO A 2 3/2 ←X 2 3/2 electronic transition. We use the IO absorption cross section measured by Hönninger (1999), scaled to Bloss et al (2001), spectrally aligned to the NO 2 absorption cross section of Harder et al (1997), and convolved to our spectral resolution. Hönninger (1999) recorded the IO absorption cross section at a spectral resolution of 0.09 nm (full width at half maximum (FWHM)) and found a peak cross section of 2.6×10 −17 cm 2 of the 4←0 vibrational band at 427.2 nm.…”