Estimated Products in Thessaloniki from a NILU-UV multichannel radiometer Zempila M.M. 1 *, Kouremeti N. 1,2 , Bais A. 1 , Meleti C. 1 , Fountoulakis I. 1 1 Laboratory of atmospheric Physics, Physics Department, Aristotle University of Thessaloniki, Greece 2 Physikalisch-Meteorologisches Observatorium Davos, Switzerland *corresponding author e-mail: mzempila@auth.gr Abstract Thessaloniki represents one of the main stations of the Greek UV Network, equipped with a NILU-UV multi-filter radiometer, 2 Brewer spectroradiometers and a YES UVB-1 actinometer. Since NILU-UV instruments can provide measurements at 5 wavelength bands, their data can be used to produce the total ozone column (TOC), the CIE-weighted irradiance (CIE) and the dose relevant to vitamin D production (Vitamin D dose). With appropriate methodologies the first 3 products can be estimated also by the Brewer and YES UVB-1 instruments. Additionally, UV irradiances, TOC and CIE are compared with estimates from the OMI instrument onboard the AURA satellite. Although the TOC estimations of NILU-UV are coherent with both ground-based and satellite data, a significant overestimation (up to 40%) is observed for the OMI UV irradiances and CIE doses. For the ground-based derived data, NILU-UV seems to overestimate by 8% and 9% the CIE and vitamin D dose with respect to the doses calculated from the YES UVB-1 actinometer. 1 Introduction The national UV monitoring network of Greece (www.uvnet.gr) was established at the end of 2004 and it was equipped with NILU-UV multi-filter radiometers. It was designed to cover geographically Greece and Cyprus with nine stations distributed at locations representing different environments. The NILU-UV instrument provides irradiance measurements at 5 wavelength bands which can be used to derive various products, among them the TOC, the CIE and Vitamin D dose. These products are also derived from the 2 Brewer spectroradiometers and the actinometer YES UVB-1 operating at the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki by applying suitable methodologies depending on the type of instrument and the available spectral information. A six-year (2005-2010) dataset of common measurements is used to derive the various products and to estimate the uncertainties introduced by the different methods applied. In addition, the total ozone column, the erythemal irradiance and the spectral irradiance at single wavelengths derived from the NILU-UV instrument are compared with corresponding estimates from the OMI (Ozone Mapping Spectrometer) satellite instrument.