Total column ozone content and aerosol optical thickness measurements: instrument performance analysis

Abstract

Measurements of total ozone content (TOC) and aerosol optical thickness (AOT) at 1020 nm are fulfilled with microprocessor-controlled hand-held ozonometer MICROTOPS (MTOPS) #7351 at the ground-based station at the Institute of Applied Physics since July 2003. It was shown that MTOPS readings are very sensitive to errors resulting from mispointing of the instrument to the Sun. The errors in retrieved TOC values may reach up to 50% depending on Sun’s spot position in the sun targeting window of the ozonometer. MTOPS calibration characteristics are analyzed with the Langley calibration plots for clear cloudless days at the Chisinau site. Variability of evaluated calibration characteristics of instrument during period of observation consists of less than 2%. AOT values at 1020 nm retrieved from MTOPS measurements are found to be smaller than AOT from CIMEL sunphotometer operating at the Chisinau site within framework of the Aerosol Robotic Network (AERONET) under the supervision of NASA/GSFC. Discrepancy between AOT values from MTOPS and CIMEL consists, on an average, ~0.028 and this is due to the absence of temperature correction of 1020 nm channel of MTOPS. Mean ratio of daily TOC from Total Ozone Mapping Spectrometer (TOMS) aboard of Earth Probe (EP) satellite divided by TOC from MTOPS and mean ratio of daily TOC from Ozone Monitoring Instrument (OMI) aboard of Aura satellite divided by TOC from MTOPS is 0.960 and 0.990, respectively.