Ring effect studies: Rayleigh scattering, including molecular parameters for rotational Raman scattering, and the Fraunhofer spectrum

Abstract

Improved parameters for the description of Rayleigh scattering in air and for the detailed rotational Raman scattering component for scattering by O(2) and N(2) are presented for the wavelength range 200-1000 nm. These parameters enable more accurate calculations to be made of bulk molecular scattering and of the Ring effect for a variety of atmospheric radiative transfer and constituent retrieval applications. A solar reference spectrum with accurate absolute vacuum wavelength calibration, suitable for convolution with the rotational Raman spectrum for Ring effect calculations, has been produced at 0.01-nm resolution from several sources. It is convolved with the rotational Raman spectra of O(2) and N(2) to produce an atmospheric Ring effect source spectrum.

The version 3 OMI NO<sub>2</sub> standard product

“…Conventional DOAS relies on very precise wavelength calibration and simultaneously determines the trace gas absorptions and magnitude of the inelastic rotational Raman (RR) scattering effect (Chance and Spurr, 1997;Grainger and Ring, 1962;Joiner et al, 1995). However, it is quite sensitive to the selection of the spectral fitting window; to the order of the closure polynomial; and, most of all, to even a slight misregistration between the radiance and irradiance wavelengths.…”

“…To account for the RR line-filling patterns, we use a linear combination of the atmospheric (Joiner et al, 1995) and the liquid-water (Vasilkov, 2002) RR spectra, convolved with the wavelength-and crosstrack-dependent OMI spectral transfer function (Dobber et al, 2006). Other steps in the algorithm include the estimation of, and correction for, spectral under-sampling patterns (Chance et al, 2005) and aggressive suppression of instrumental noise.…”

Retrieval of global mesospheric sodium densities from the Odin satellite

“…We use results on the Fraunhofer minima from McNutt and Mack [1963] and normalize them to the absolute photon fluxes provided by Chance and Spurr [1997]. Varying shifts of the solar Fraunhofer structure due to the Earth's motion and the Sun's gravitational red-shift must be taken into account [McNutt and Mack, 1963].…”

“…[14] The Ring effect is of potential importance for Na retrievals as it increases the photon flux in the Na D Fraunhofer minima [Chance and Spurr, 1997]. This provides additional illumination of the mesospheric sodium layer at the Na D resonance wavelengths.…”

Ground‐based measurements of ozone and NO2during MANTRA 1998 using a Zenith‐sky spectrometer

“…Next, differential cross-sections of absorbing gases (derived by subtracting a second-order polynomial from laboratory cross-sections) were simultaneously fitted to the differential spectrum using a nonlinear (Marquart-Levenberg) least-squares fitting routine (Press et al, 1992). The Ring effect was treated as a quasi-linear absorber in cross-section space using a modelled Ring cross-section calculated by Chance and Spurr (1997). An iterative shifting and stretching algorithm was used to correct small changes in wavelength calibration and spectral dispersion of the spectrometer.…”