Erschienen in:
Atmospheric Measurement Techniques, 11 (2018) 7, Seite 4059-4072
Sprache:
Englisch
DOI:
10.5194/amt-11-4059-2018
ISSN:
1867-8548
Entstehung:
Anmerkungen:
Beschreibung:
Abstract. Total ozone column measurements can be made using Brewer spectrophotometers,which are calibrated periodically in intercomparison campaigns with respectto a reference instrument. In 2003, the Regional Brewer Calibration Centrefor Europe (RBCC-E) was established at the Izaña Atmospheric ResearchCenter (Canary Islands, Spain), and since 2011 the RBCC-E has transferred itscalibration based on the Langley method using travelling standard(s) that arewholly and independently calibrated at Izaña. This work is focused onreporting the consistency of the measurements of the RBCC-E triad (Brewerinstruments #157, #183 and #185) made at the Izaña AtmosphericObservatory during the period 2005–2016. In order to study the long-termprecision of the RBCC-E triad, it must be taken into account that each Brewertakes a large number of measurements every day and, hence, it becomesnecessary to calculate a representative value of all of them. This value wascalculated from two different methods previously used to study the long-termbehaviour of the world reference triad (Toronto triad) and Arosa triad.Applying their procedures to the data from the RBCC-E triad allows thecomparison of the three instruments. In daily averages, applying theprocedure used for the world reference triad, the RBCC-E triad presents arelative standard deviation equal to σ = 0.41 %, which iscalculated as the mean of the individual values for each Brewer(σ157 = 0.362 %, σ183 = 0.453 % andσ185 = 0.428 %). Alternatively, using the procedure usedto analyse the Arosa triad, the RBCC-E presents a relative standard deviationof about σ = 0.5 %. In monthly averages, the method used forthe data from the world reference triad gives a relative standard deviationmean equal to σ = 0.3 % (σ157 = 0.33 %,σ183 = 0.34 % and σ185 = 0.23 %).However, the procedure of the Arosa triad gives monthly values ofσ = 0.5 %. In this work, two ozone data sets are analysed:the first includes all the ozone measurements available, while the secondonly includes the simultaneous measurements of all three instruments.Furthermore, this paper also describes the Langley method used to determinethe extraterrestrial constant (ETC) for the RBCC-E triad, the necessary firststep toward accurate ozone calculation. Finally, the short-term or intradayconsistency is also studied to identify the effect of the solar zenith angleon the precision of the RBCC-E triad.