Total ozone content over KYIV-GOLOSEYEV station by ground-based and satellite measurements in 2010–2015

1Grytsai, AV, 2Milinevsky, GP
1Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
2Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Space Sci.&Technol. 2018, 24 ;(3):40-54
Section: Space and Atmospheric Physics
Publication Language: Ukrainian
Ground-based measurements of total ozone content (TOC) in Dobson Units (DU) over Kyiv-Goloseyev station using Dobson spectrophotometer are carried out from May 2010. The ground-based measurements are realized under Direct Sun (DS), Zenith Blue (ZB), and Zenith Cloud (ZC) conditions in the standard pairs of wavelengths A, C, D in near ultraviolet range (300—340 nm).
            In this work, the discrepancies between satellite and ground-based TOC observations in the atmosphere over the station are studied. Besides, both seasonal TOC variations and changes in the differences between satellite and ground-based measurements are considered. First task of the work is to study main features of the seasonal TOC variations at Kyiv-Goloseyev station. Second task is to estimate the level of distinctions between satellite and ground-based TOC values and to determine possible causes of the distinctions. We processed the Kyiv-Goloseyev Dobson DS, ZB, and ZC double-pair (AD and CD) measurements of total ozone content using the Satellite OMI/Aura, GOME-2/MetOpA, and GOME-2/MetOpB data. For the comparison, both separate measurements made in the vicinity of the ground-based station and the corresponding models with 6-hour step were considered. The differences between satellite (model) and ground-based data are studied separately for each type of the Dobson observations.
            It was determined that minimal annual mean TOC values were registered in 2011 (319—322 DU in dependence on measurement type) and maximal values were reached in 2013 (327—338 DU). The difference between the satellite and ground-based data has exhibited a seasonal cycle with relative TOC underestimation in the ground-based measurements at the late autumn and early winter. A decrease in the DSAD values near the winter solstice moment is seen as the main cause of the underestimation. Firstly, an indicated phenomenon worsens the AD data quality because of the fast decrease of radiation intensity in the short-wave A pair, what happens when solar zenith angle rises, and scattered light has a greater impact. Typical values of the discrepancy reach 20 DU and sometimes even greater. Discrepancies increase with high ozone content above 400 DU. On the contrary, the CD values are overestimated under those conditions as compared with model ones.   According to the results of comparison with satellite measurements, the Kyiv-Goloseyev Dobson spectrophotometer No. 040 demonstrates the high quality in cases of DSAD, DSCD, and ZBAD series (excluding DSCD in 2015). The ZBCD and ZC data seem to be unsteady for mean differences, and double standard deviations calculated during a calendar year regularly exceed 25 DU.
Keywords: data comparison, Dobson spectrophotometer, observational series, satellite measurements, total ozone content
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