Direct-Sun column ozone retrieval by the ultraviolet multifilter rotating shadow-band radiometer and comparison with those from Brewer and Dobson spectrophotometers

Abstract

A methodology for direct-Sun ozone retrieval using the ultraviolet multifilter rotating shadow-band radiometer (UV-MFRSR) is presented. Total vertical column ozone was retrieved in three stations: Mauna Loa, Hawaii, in the U.S., and Regina, Saskatchewan, and Toronto, Ontario, in Canada, from direct solar irradiances of the UV-MFRSR at 325-, 305-, 332-, and 311-nm channels (2-nm FWHM). The total uncertainty of ozone retrievals in this study is +/-2.0%. For Mauna Loa the mean ratios of the UV-MFRSR column ozone retrievals to the collocated Dobson and Brewer were 0.998 and 0.986 between May and September of 1999. The mean ratio of UV-MFRSR retrievals to the collocated Brewer retrievals was 1.012 in Toronto between April and August of 1999, and the mean ratio of retrievals of the UV-MFRSR to the collocated Brewer was 0.988 in Regina between June and September of 1999. Total vertical column ozone values for solar zenith angles of >70 degrees were not considered, because of the signal-to-noise ratio and the angular response of the instruments, and were not used in the evaluation. The advantages of total vertical column ozone retrieval using UV-MFRSR include relatively low cost, computer-controlled operation, automated calibration stability checks, and minimal maintenance. It allows for the real-time measurement of total vertical column ozone. The UV-MFRSR is being used at 28 sites across the United States and 2 sites in Canada that form the U.S. Department of Agriculture UV-B Radiation Monitoring and Research Program. This constitutes a unique network of total vertical colunm ozone measurement.

Surface ultraviolet radiation

“…These instruments are often equipped with a shadow-band, which allows the determination of both direct and diffuse components of surface irradiance. Direct data can then be used to calculate total ozone (Gao et al, 2001), optical depth of thin clouds (Min et al, 2004), aerosol optical depth (Krotkov et al, 2005a), aerosol single scattering albedo (Petters et al, 2003;Goering et al, 2005;Krotkov et al, 2005b), and reconstructed direct spectra with the aid of radiative transfer modelling (Min and Harrison, 1998).…”

Comparison of total column ozone data from ground‐based MFRSR measurements taken in the southern U.S. region with OMI satellite retrievals

“…[7] The UV-MFRSR has been established as a reliable TCO measurement instrument through comparison studies with Brewer and Dobson spectrophotometers [Slusser et al, 1999;Bigelow and Slusser, 2000;Gao et al, 2001]. The direct-Sun irradiance method is employed to retrieve the TCO and is explained fully by Gao et al [2001], who calculated the total uncertainty in TCO retrievals by the UV-MFRSR instrument to be ±2.0%.…”

Spatial Statistical Analyses of Global Trends of Ultraviolet B Fluxes in the Continental United States

“…Spaceborne observations can also provide information about two key parameters that determine UV irradiance: total ozone amount and the cloud transmittance, or reflectivity. Consequently, TOMS, which has provided both total ozone and cloud reflectivity measurements since the late 1970s, is an important source of derived UV data (Lapeta et al, 2000;Gao et al, 2001;Fioletov et al, 2002). Clouds that are intimately linked with precipitation have a large influence on the surface energy budget and evapotranspiration; thus, clouds may be used as a global index to address long-term climate change.…”

“…Gao et al (2001) developed a methodology for direct-sun ozone retrieval using the ultraviolet multifilter rotating shadow-bandradiometer (UV-MFRSR). This approach allows the real-time measurement of total vertical column ozone at ground-based stations; three such stations were tracked in this study.…”