Total column ozone retrieval from a novel array spectroradiometer

Abstract. This study presents a new total column ozone (TCO) retrieval from the Koherent system, developed at Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center (PMOD/WRC). The instrument is based on small, cost-effective, robust, low-maintenance and state-of-the-art-technology array spectroradiometer. It consists of BTS-2048-UV-S-F spectroradiometer Gigahertz-Optik GmbH, coupled with an optical fibre to lens-based telescope mounted sun tracker for measuring direct UV irradiance in ultraviolet wavelength band between 305 345 nm. Two different algorithms are retrieving TCO these spectral measurements: (1) retrieved by least-squares-fit algorithm (LSF) (2) custom-double-ratio (CDR) technique using four specifically selected wavelengths measurements. double-ratio analogous applied Dobson instruments Brewer but adopted here Koherent. was calibrated two ways: (a) absolute calibration spectra portable reference radiation QASUME LSF (b) relative extraterrestrial constant (ETC) CDR minimising slope air mass differences adjustment ETC allows be standard during campaigns, such as double-monochromator Brewer. A 2-year comparison Switzerland, 156 (double monochromator) shows that derived agree, average, over entire period within 0.7 % all retrievals terms offset. performance slant path depends corrections. stray-light-corrected exhibits smaller dependency than performs almost well system. comparable single monochromator. combination both leads offset close zero compared 156, seasonal amplitude difference 0.08 maximum 1.64 %, which similar other or Dobson. Applying selecting slit functions Dobson, respectively, determination effective temperature uncertainty 3 K daily averages. With improved retrieval, serves could also used monitor remote sites. presented may array-based spectroradiometers, providing measurements band.