A climatology of aerosol optical depths in the ultraviolet wavelengths for Hobart, Australia, as determined by a Brewer MKIII spectrophotometer

Abstract

The study examines aerosol optical depth (AOD) measurements at 320 nm wavelength by a Brewer MKIII spectrophotometer located in Hobart, Australia. A climatology was developed from records encompassing the period April 4, 2002, to February 27, 2019. A methodology is described to extract cloudless episodes and cloudless half-days. Extraterrestrial irradiances are obtained using a travelling calibration standard and are supplemented by Langley analyses on cloudless and stable half-days. AODs are obtained by applying Beer's law to every reading and subtracting known values of ozone optical depth and Rayleigh scatter. Statistics are provided on the daily, monthly and interannual variability. Concurrent measurements from a Multifilter Rotating Shadowband Radiometer (MFRSR) operating in the visible band enabled the spectral variability of AOD to be determined. They showed the dominance of oceanic aerosols but with some input from land-based aerosols originating mostly from biomass burning.