Aerosol Optical Depth and the Global Brewer Network: A Study Using U.K.- and Malaysia-Based Brewer Spectrophotometers

Kumharn, Wilawan; Rimmer, John; Smedley, Andrew R. D.; Ying, Toh Ying; Webb, Ann R.

doi:10.1175/jtech-d-11-00029.1

Cited by 19 publications

(20 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Bais, 1997;Marenco et al, 1997;Carvalho and Henriques, 2000) in both the ultraviolet (UV) range (all models) and the visible part of the solar spectrum (MkIV and MkV models only). At least two hundred Brewer spectrophotometers are operating all over the world (Kumharn et al, 2012), thus constituting a dense network that can be profitably exploited to gain valuable past and present information about aerosols. To this end, the efforts in the framework of a recently started COST Action (EUBREWNET, http://www.eubrewnet.org/cost1207/) are focusing, among other topics, on standardising the AOD retrieval algorithm and developing the necessary quality assurance/quality control protocols.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

View full text Add to dashboard Cite

Abstract.A MkIV Brewer spectrophotometer has been operating in Athens since 2004. Direct-sun measurements originally scheduled for nitrogen dioxide retrievals were reprocessed to provide aerosol optical depths (AODs) at a wavelength of about 440 nm. A novel retrieval algorithm was specifically developed and the resulting AODs were compared to those obtained from a collocated Cimel filter radiometer belonging to the Aerosol Robotic Network (AERONET). The series are perfectly correlated, with Pearson's correlation coefficients being as large as 0.996 and with 90 % of AOD deviations between the two instruments being within the World Meteorological Organisation (WMO) traceability limits. In order to reach such a high agreement, several instrumental factors impacting the quality of the Brewer retrievals must be taken into account, including sensitivity to the internal temperature, and the state of the external optics and pointing accuracy must be carefully checked. Furthermore, the long-term radiometric stability of the Brewer was investigated and the performances of in situ Langley extrapolations as a way to track the absolute calibration of the Brewer were assessed. Other sources of error, such as slight shifts of the wavelength scale, are discussed and some recommendations to Brewer operators are drawn. Although MkIV Brewers are rarely employed to retrieve AODs in the visible range, they represent a key source of information about aerosol changes in the past three decades and a potential worldwide network for present and future coordinated AOD measurements. Moreover, a better understanding of the AOD retrieval at visible wavelengths will also contribute in improving similar techniques in the more challenging UV range.

show abstract

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Nowadays, the Brewer network consists of about 195 instruments installed in 44 different countries throughout the world (Kumharn et al, 2012). Among them, according to the metadata archive of the World Ozone and Ultraviolet radiation Data Center (WOUDC, http: //woudc.org/data/MetaQuery/metaquery_e.cfm), more than 60 MKIV Brewer spectrophotometers have been put in operation and long-term nitrogen dioxide records have been collected at the respective stations.…”

Section: Introductionmentioning

confidence: 99%

Improved retrieval of nitrogen dioxide (NO<sub>2</sub>) column densities by means of MKIV Brewer spectrophotometers

et al. 2014

View full text Add to dashboard Cite

Abstract.A new algorithm to retrieve nitrogen dioxide (NO 2 ) column densities using MKIV ("Mark IV") Brewer spectrophotometers is described. The method includes several improvements, such as a more recent spectroscopic data set, the reduction of measurement noise, interference by other atmospheric species and instrumental settings, and a better determination of the zenith sky air mass factor. The technique was tested during an ad hoc calibration campaign at the high-altitude site of Izaña (Tenerife, Spain) and the results of the direct sun and zenith sky geometries were compared to those obtained by two reference instruments from the Network for the Detection of Atmospheric Composition Change (NDACC): a Fourier Transform Infrared Radiometer (FTIR) and an advanced visible spectrograph (RASAS-II) based on the differential optical absorption spectrometry (DOAS) technique. To determine the extraterrestrial constant, an easily implementable extension of the standard Langley technique for very clean sites without tropospheric NO 2 was developed which takes into account the daytime linear drift of stratospheric nitrogen dioxide due to photochemistry. The measurement uncertainty was thoroughly determined by using a Monte Carlo technique. Poisson noise and wavelength misalignments were found to be the most influential contributors to the overall uncertainty, and possible solutions are proposed for future improvements. The new algorithm is backward-compatible, thus allowing for the reprocessing of historical data sets.

show abstract

“…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: 80%

“…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%

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

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Aerosol Optical Depth and the Global Brewer Network: A Study Using U.K.- and Malaysia-Based Brewer Spectrophotometers

Cited by 19 publications

References 36 publications

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

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

Improved retrieval of nitrogen dioxide (NO<sub>2</sub>) column densities by means of MKIV Brewer spectrophotometers

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

Contact Info

Product

Resources

About

Aerosol Optical Depth and the Global Brewer Network: A Study Using U.K.- and Malaysia-Based Brewer Spectrophotometers

Cited by 19 publications

References 36 publications

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

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

Improved retrieval of nitrogen dioxide (NO&lt;sub&gt;2&lt;/sub&gt;) column densities by means of MKIV Brewer spectrophotometers

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

Contact Info

Product

Resources

About

Improved retrieval of nitrogen dioxide (NO<sub>2</sub>) column densities by means of MKIV Brewer spectrophotometers