Effective Bass‐Paur 1985 ozone absorption coefficients for use with Dobson ozone spectrophotometers

Abstract

Details are presented concerning the derivation of new, standard, effective ozone absorption coefficients for use with Dobson ozone spectrophotometers. The work was performed under auspices of the World Meteorological Organization (WMO) Global Ozone Research and Monitoring Program, with the goal of improving and standardizing ozone measurements throughout the world. The new coefficients, based on the laboratory measurements of Bass and Paur (1985), were sanctioned for use worldwide, beginning January 1, 1992, by the WMO Executive Panel on Environmental Pollution and Atmospheric Chemistry. The new coefficients, together with use of slightly improved Rayleigh molecular scattering coefficients also adopted as standard, yield total ozone amounts 2.6% smaller than values obtained during July 1, 1957 to December 31, 1991, derived from the use of Vigroux (1953, 1967) ozone absorption coefficients. Information is provided also on correcting ozone data obtained in the past to the new ozone absorption coefficient scale. 1. INTRODUCTION Early Dobson ozone spectrophotometer observations were processed using ozone absorption coefficients based on the laboratory data of Ny and Choong [1933]. At the beginning of the International Geophysical Year (IGY) (July 1, 1957), new absorption coefficients were adopted for use [Dobson, 1957a], employing the laboratory values of Vigroux [1953]. Pre-IGY Dobson spectrophotometer ozone values were converted to the Vigroux [1953] scale by multiplying them by 1.36. Because the Vigroux [1953] coefficients (Table 1) gave inconsistent ozone values from observations on different combinations of wavelengths (e.g., CD-wavelength and ABwavelength observations yielded 10% less and 13% more ozone, respectively, than did AD-wavelength observations), the Vigroux AD-wavelength ozone absorption coefficients were adopted as standard. Based on a redetermination of the ozone absorption coefficients by Vigroux [1967] and an examination of the coefficients by G.M.B. Dobson in light of atmospheric observations made in Canada, the United Kingdom and elsewhere, a modified set of ozone absorption coefficients (Table 2) was derived [World Meteorological Organization (WMO), 1968] which gave highly consistent ozone amounts from observations made on different wavelengths (Table 3). These modified coefficients, which preserved the original Vigroux AD-wavelengths coefficient as standard, were recommended for use by the International 1Now at by the WMO throughout the world beginning January 1, 1968 [WMO, 1968]. Rayleigh molecular scattering coefficients used with the ozone absorption coefficients in processing ozone data were derived from the Rayleigh-Cabanes formula [Dobson, 1957a]. Komhyr [1980] reexamined the Vigroux [1953] ozone absorption coefficients and concluded that the ADwavelengths coefficient of 1.388 cm -1, adopted as standard, may be too small, causing Dobson instrument ozone values to be overestimated by up to 5%. Discussion of the problem with A. Bass (U.S. Bureau of Standards, Gaithersburg, Maryland) promp...

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

“…For Brewer instruments this is less of a concern since the ratio of the cross sections at the wavelength pairs used in these instruments is less temperature dependent. In principle, it is possible to correct for this temperature dependence in the Dobson data (Komhyr et al, 1993), but this is not done for the present work. Both types of instruments are also affected by large contributions of diffuse light when observing at solar elevations below 15 • .…”

Ozone comparison between Pandora #34, Dobson #061, OMI, and OMPS in Boulder, Colorado, for the period December 2013–December 2016

“…The Dobson instrument uses a differential absorption method to derive total column ozone from direct-sun measurements using two UV wavelength pairs in the 300-340 nm range (see Herman et al, 2015). The extensive Dobson network uses the Bass-Paur (BP) ozone absorption cross sections (Bass and Paur, 1985) for operational data processing (Komhyr et al, 1993).…”

Sensitivity of Dobson and Brewer Umkehr ozone profile retrievals to ozone cross-sections and stray light effects

“…More information on the Brewer Mark IV operations over the continental US sites, Umkehr measurements (contained in the so-called B-files) and retrieved ozone profiles can be found at the NOAA-EPA Brewer Spectrophotometer UV and Ozone Network (NEUBrew) data centre (HU www.esrl.noaa.gov/gmd/grad/neubrew UH). Ozone profiles are retrieved from the classic Brewer Umkehr measurements (manufacturer's supplied set of operational commands and programs) using a modified UMK04 algorithm (PC code, O3BUmkehr v.2.5, developed by Martin Stanek) (Petropavlovskikh et al, 2005b(Petropavlovskikh et al, , 2007 (Komhyr, 1982, Komhyr et al, 1993 and accepted as standard for all Dobson instruments deployed worldwide (Komhyr et al, 1989). Slit function (SF) for the core bandpass is centred at the nominal wavelength (λ short 0 or λ long 0 ) and is approximated as a triangular shape for the shorter wavelength of the standard Umkehr pair, while the shape of the slit function at the longer wavelength is a trapezoid.…”