28 Jun 2023
 | 28 Jun 2023
Status: a revised version of this preprint is currently under review for the journal AMT.

Novel use of a Bentham UV Double Monochromator for measurements of global and direct irradiance, ozone and aerosol

Alexander Geddes, Ben Liley, Richard McKenzie, Michael Kotkamp, and Richard Querel

Abstract. A novel ultraviolet spectrometer has been developed and tested over 10 years at Lauder, New Zealand. The system, UV2, makes alternating measurements of the global and direct UV irradiance and can therefore be used to measure ozone and aerosol optical depth. After an analysis of the stability of UV2, these measurements, along with UV irradiance are compared to relevant observations made by an additional UV spectrometer (UV4), a Dobson spectrophotometer (#72) and two radiometers measuring aerosol optical depth, a Prede skyradiometer and a Middleton Solar radiometer (SP02). UV2 irradiance is shown to be lower than UV4 by between 2.5–3.5 %, with a standard deviation of a similar magnitude. Total column ozone values are shown to agree with Dobson values with a mean bias of 2.57 Dobson units (DU) and standard deviation of 1.15 DU when using the direct sun measurements. Aerosol optical depth at 400–412 nm and 500 nm agrees to within 0.015 and is comparable to the difference between the reference radiometers. Further work is needed, particularly in the radiometric calibration at longer wavelengths, in order to determine if this instrument can supersede or enhance measurements made by the Dobson or the aerosol radiometers.

Alexander Geddes et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2023-107', Anonymous Referee #1, 07 Jul 2023
    • AC1: 'Reply on RC1', Alex Geddes, 08 Nov 2023
  • RC2: 'RC on amt-2023-107', Anonymous Referee #2, 08 Sep 2023
    • AC2: 'Reply on RC2', Alex Geddes, 08 Nov 2023

Alexander Geddes et al.

Alexander Geddes et al.


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Short summary
In this paper we describe a unique spectrometer that has been developed and tested over 10 years at Lauder, New Zealand. The spectrometer in question, UV2, makes alternating measurements of global UV and direct sun UV irradiance. After an assessment of the instruments performance, we compare the ozone and aerosol optical depth derived from UV2 to other, independent measurements, finding excellent agreement suggesting that UV2 could supersede these measurements, particularly for ozone.