Retrieval of aerosol optical depth in the visible range with a Brewer spectrophotometer in Athens

Diémoz, Henri; Eleftheratos, Kostas; Kazadzis, Stelios; Amiridis, Vassilis; Zerefos, C. S.

doi:10.5194/amt-9-1871-2016

Cited by 19 publications

(24 citation statements)

References 63 publications

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“…Brewer ozone data for Athens have been analyzed in recent studies [51,52]. In addition, the instrument was used to derive AOD in the visible part of the solar spectrum [53]. For the first time in this study, we analyzed spectral UV irradiance measurements at 324 nm from the Athens Brewer instrument, for the period January 2009 to December 2014.…”

Section: Brewer Spectrophotometermentioning

confidence: 99%

Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

et al. 2018

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The absorbing and scattering nature of aerosols affects the total radiative forcing and is quantified by single scattering albedo (SSA), which is defined as the absorption to total extinction ratio. There are limited measurements of SSA in the ultraviolet (UV) irradiance spectrum, hence, the influence of SSA on incoming UV irradiance has not been explored in great depth. In the present study, UV irradiance was calculated and compared using different SSA datasets retrieved at Athens, Greece during 2009–2014; including SSA time series from Ultraviolet Multi-Filter Radiometer (UVMFR) at 332 and 368 nm, SSA from AERONET at 440 nm, from OMI satellite at 342.5 nm and AeroCom climatological database at 300 nm. Irradiances were estimated using a radiative transfer model (RTM). Comparisons of these results revealed that relative differences of UVA and UVB could be as high as 20%, whilst average relative differences varied from 2% to 8.7% for the entire experimental period. Both UVA and UVB drop by a rate of ~12% for 0.05 aerosol absorption optical depth in comparison to ones estimated with the use of SSA at visible range. Brewer irradiance measurements at 324 nm were used to validate modeled monochromatic irradiances and a better agreement was found when UVMFR SSAs were used with an average difference of 0.86%. However, when using visible or climatological input, relative differences were estimated +4.91% and +4.15% accordingly.

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Section: Brewer Spectrophotometermentioning

confidence: 99%

Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

et al. 2018

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“…In the comparison between Brewer and OMI data the scaled correlation (RHOs) was calculated (Diémoz et al, 2016) to exclude the possibility that the source of the correlation is a common cycle (e.g. the annual cycle).…”

Section: Statistical Parametersmentioning

confidence: 99%

Examination on total ozone column retrievals by Brewer spectrophotometry using different processing software

et al. 2018

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Abstract. The availability of long-term records of the total ozone content (TOC) represents a valuable source of information for studies on the assessment of short- and long-term atmospheric changes and their impact on the terrestrial ecosystem. In particular, ground-based observations represent a valuable tool for validating satellite-derived products. To our knowledge, details about software packages for processing Brewer spectrophotometer measurements and for retrieving the TOC are seldom specified in studies using such datasets. The sources of the differences among retrieved TOCs from the Brewer instruments located at the Italian stations of Rome and Aosta, using three freely available codes (Brewer Processing Software, BPS; O3Brewer software; and European Brewer Network (EUBREWNET) level 1.5 products) are investigated here. Ground-based TOCs are also compared with Ozone Monitoring Instrument (OMI) TOC retrievals used as an independent dataset since no other instruments near the Brewer sites are available. The overall agreement of the BPS and O3Brewer TOC data with EUBREWNET data is within the estimated total uncertainty in the retrieval of total ozone from a Brewer spectrophotometer (1 %). However, differences can be found depending on the software in use. Such differences become larger when the instrumental sensitivity exhibits a fast and dramatic drift which can affect the ozone retrievals significantly. Moreover, if daily mean values are directly generated by the software, differences can be observed due to the configuration set by the users to process single ozone measurement and the rejection rules applied to data to calculate the daily value. This work aims to provide useful information both for scientists engaged in ozone measurements with Brewer spectrophotometers and for stakeholders of the Brewer data products available on Web-based platforms.

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“…Kouremeti et al (2014) found percentages between 46 and 88 % when comparing independently calibrated Brewer and Cimel instruments at wavelengths between 306 and 320 nm (extrapolated from 340 nm in the case of the Cimel). Diémoz et al (2016) calibrated a Mk IV Brewer with respect to a Cimel instrument at 437 nm, finding that 90 % of the observations were within the WMO traceability limit once a temperature correction for the Brewer was included. Carlund et al (2017) reported percentages between 85.6 and 97 % between UVPFR and Brewer photometers operating in the 306-320 nm range, the Brewer being calibrated using the UVPFR's AOD as reference.…”

Section: Brewermentioning

confidence: 99%

“…Previous works have already demonstrated the feasibility of using Brewer spectrophotometers, usually devoted to the measurement of the total ozone column (TOC) and UV irradiance, to determine the aerosol optical depth (AOD); see, e.g., Harrison and Michalsky (1994), , Marenco et al (1997), Carvalho and Henriques (2000), , Marenco et al (2002), Cheymol and De Backer (2003), Arola and Tapani (2004), Gröbner and Meleti (2004), Savastiouk and McElroy (2004a), Savastiouk and McElroy (2004b), Silva and Kirchhoff (2004), Kazadzis et al (2005), Savastiouk (2006), Sellitto et al (2006), Kazadzis et al (2007), De Bock et al (2010), Kumharn (2010), Kumharn et al (2012), De Bock et al (2014), Kumharn et al (2015), Rodriguez-Franco (2015), Diémoz et al (2016), and Kumharn and Hanprasert (2016). Although Brewer spectrophotometers can be used to retrieve AOD at longer wavelengths, in their standard operational mode most instruments can only produce data in the 300-320 nm range.…”

Section: Introductionmentioning

confidence: 99%

Answers to RC5

López-Solano¹

2018

Preprint

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Aerosols play an important role in key atmospheric processes and feature high spatial and temporal variabilities. This has motivated scientific interest in the development of networks capable of measuring aerosol properties over large geographical areas in near-real time. In this work we present and discuss results of an aerosol optical depth (AOD) algorithm applied to instruments of the European Brewer Network. This network is comprised of close to 50 Brewer spectrophotometers, mostly located in Europe and adjacent areas, although instruments operating at, for example, South America and Australia are also members. Although we only show results for instruments calibrated by the Regional Brewer Calibration Center for Europe, the implementation of the AOD algorithm described is intended to be used by the whole network in the future. Using data from the Brewer intercomparison campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sun photometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and, for well-maintained instruments, a stability similar to that of the ozone measurements. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of AOD.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Retrieval of aerosol optical depth in the visible range with a Brewer spectrophotometer in Athens

Cited by 19 publications

References 63 publications

Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

Examination on total ozone column retrievals by Brewer spectrophotometry using different processing software

Answers to RC5

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