Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval

Kazadzis, Stelios; Bais, A. F.; Kouremeti, Natalia; Gerasopoulos, E.; Garane, Katerina; Blumthaler, M.; Schallhart, B.; Cede, Alexander

doi:10.1364/ao.44.001681

Cited by 82 publications

(84 citation statements)

References 43 publications

(50 reference statements)

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“…At the same time, the estimated 2σ uncertainty at 305 nm is still only about half of estimates by Kazadzis et al (2005), who estimated 1σ uncertainty at UVB wavelengths to 0.07. It is therefore considered useful to continue working on AOD even at 305-306 nm to learn more on AOD retrievals in the UVB.…”

Section: Total Uvpfr Aod Uncertaintymentioning

confidence: 82%

“…An additional very likely reason for the good agreement is the fact that both instrument types measure at close wavelengths in the UVB. In earlier studies in which AOD was determined from Brewer DS measurements the validation has so far only been done against measurements at UVA or even VIS wavelengths (Marenco et al, 2002;Cheymol and De Backer, 2003;Cheymol et al, 2006;Gröbner and Meleti, 2004;Kazadzis et al, 2005Kazadzis et al, , 2007De Bock et al, 2010;Kumharn et al, 2012). Also, earlier comparisons of AOD from Brewers of different type have shown larger differences than between the UVPFR and the MkIII Brewer in this study (Kazadzis et al, 2005;Kumharn et al, 2012).…”

mentioning

confidence: 78%

“…The Brewer spectrophotometer is an instrument initially designed for providing total column ozone (TCO) measurements based on the use of direct sun (DS) irradiance measured at specific wavelengths in the short UVA and in the UVB range (e.g., Kerr et al, 1985). During the past years, several attempts have been presented in the literature, which showed the use of the abovementioned Brewer measurements in order to retrieve AOD in the UVB (e.g., Marenco et al, 1997Marenco et al, , 2002Cheymol and De Backer, 2003;Cheymol et al, 2006;Gröbner and Meleti, 2004;Kazadzis et al, 2005Kazadzis et al, , 2007Meleti et al, 2009;De Bock et al, 2010Kumharn et al, 2012). In addition, Arola and Koskela (2004) have discussed the uncertainties and possible systematic errors linked with the Brewer related DS retrieval for AOD.…”

Section: Introductionmentioning

confidence: 99%

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Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

et al. 2017

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Abstract. The determination of aerosol properties, especially the aerosol optical depth (AOD) in the ultraviolet (UV) wavelength region, is of great importance for understanding the climatological variability of UV radiation. However, operational retrievals of AOD at the biologically most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR (UV precision filter radiometer) sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high-altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V 0 ) derived from Langley plot calibrations underestimate the true extraterrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument's spectral response functions also result in an apparent air-mass-dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore introduced. Langley calibrations performed 13-14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a high-accuracy standard precision filter radiometer, measuring AOD at 368-862 nm wavelengths, showed consistent results. Also, very good agreement was achieved by comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB is higher than that reported from AOD instruments measuring in UVA and visible ranges. However, the precision can be high among instruments using harmonized algorithms for ozone and Rayleigh optical depth as well as for air mass terms. For 4 months of comparison measurements with the UVPFR and a Brewer, the root mean squared AOD differences were found < 0.01 at all the 306-320 nm Brewer wavelengths.

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Section: Total Uvpfr Aod Uncertaintymentioning

confidence: 82%

mentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

et al. 2017

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“…Research also shows that the standard Brewer direct sun (DS) measurements allow AOD retrieval at the wavelengths used for ozone determination (mainly 320.1 nm). Some authors base their retrieval on the absolute calibration of the solar spectral irradiance measured by the Brewer (Bais, 1997;Marenco et al, 1997;Kazadzis et al, 2005) whereas others use the Langley extrapolation method to determine the absolute calibration of the irradiance (Kirchhoff et al, 2001;Marenco et al, 2002;Cheymol and De Backer, 2003). Arola and Koskela (2004) discussed the systematic errors in the AOD retrieval from Brewer DS measurements, which led to improvements of the conventional Langley Plot Method (e.g.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Optical Depth measurements at 340 nm with a Brewer spectrophotometer and comparison with Cimel sunphotometer observations at Uccle, Belgium

et al. 2010

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Abstract. The Langley Plot Method (LPM) is adapted for the retrieval of Aerosol Optical Depth (AOD) values at 340 nm from Brewer#178 sun scan measurements between 335 and 345 nm (convoluted with the band pass function of the Cimel sunphotometer filter at 340 nm) performed in Uccle, Belgium. The use of sun scans instead of direct sun measurements simplifies the comparison of the AOD values with quasi-simultaneous Cimel sunphotometer values. Also, the irradiance at 340 nm is larger than the one at 320.1 nm due to lower ozone absorption, thus improving the signal to noise ratio. For the selection of the cloudless days (from now on referred to as calibration quality clear days), a new set of criteria is proposed. With the adapted method, individual clear sky AOD values, for which the selection criteria are also presented in this article, are calculated for a period from September 2006 until the end of August 2010. These values are then compared to quasi-simultaneous Cimel sunphotometer measurements, showing a very good agreement (the correlation coefficient, the slope and the intercept of the regression line are respectively 0.974, 0.968 and 0.011), which proves that good quality observations can be obtained from Brewer sun scan measurements at 340 nm. The analysis of the monthly and seasonal Brewer AODs at Uccle is consistent with studies at other sites reporting on the seasonal variation of AODs in Europe. The highest values can be observed in summer and spring, whereas more than 50% of the winter AODs are lower than 0.3. On a monthly scale, the lowest AOD are observed in December and the highest values occur in June and April. No clear weekly cycle is observed for Uccle. The current cloud-screening algorithm is still an issue, Correspondence to: V. De Bock (veerle.debock@meteo.be) which means that some AOD values can still be influenced by scattered clouds. This effect can be seen when comparing the calculated monthly mean values of the Brewer with the AERONET measurements.

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“…Even if such information is limited, this approach is still useful since it potentially makes possible to determine AOD for about 200 instruments: some of them have 15-20 years long records. The method was developed and described in previous studies (Marenco et al, 1997;Carvhallo and Henriques, 2000;Gröbner et al, 2001;Cheymol and De Backer, 2003;Bais et al, 2004;Kazadzis et al,2005). Validation studies have also already been done (Gröbner and Meleti 2004;Jaroslawski and Krzyscin, 2005;Savastiouk and Mc Elroy, 2005;Cheymol et al, 2006;Sellitto et al, 2006) to provide information on the accuracy of the AOD in the UV-B from Brewer instruments.…”

Section: Introductionmentioning

confidence: 99%

Intercomparison of Aerosol Optical Depth from Brewer Ozone spectrophotometers and CIMEL sunphotometers measurements

et al. 2009

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Abstract. The Langley plot method applied on the Brewer Ozone measurements can provide accurate Aerosol Optical Depth (AOD) in the UV-B. We present seven intercomparisons between AOD retrieved from Brewer Ozone measurements at 320 nm and AOD measured by CIMEL sunphotometer at 340 nm or 440 nm (shifted to 320 nm in using the Angström's law), which are stored in the international AERONET database. Only the intercomparisons between co-located instruments can be used to validate the Langley Plot Method applied to the Brewer measurements: in this case, all the correlation coefficients are above 0.82. If the instruments are not at the same site, the correlation between the AOD retrieved by both instruments is much lower. In applying the Angström's law the intercomparison is improved compared to previous study.

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Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval

Cited by 82 publications

References 43 publications

Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

Aerosol Optical Depth measurements at 340 nm with a Brewer spectrophotometer and comparison with Cimel sunphotometer observations at Uccle, Belgium

Intercomparison of Aerosol Optical Depth from Brewer Ozone spectrophotometers and CIMEL sunphotometers measurements

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