Uncertainty of different atmospheric ozone retrievals and its effect on temporal trends and radiative transfer simulations in the Iberian Peninsula

Abstract

Uncertainty in total ozone column (TOC) values is quantified for eight different databases through a direct comparison with ground-based data at three Spanish locations, the maximum uncertainty being about 10.5 Dobson unit. A long-term TOC series is constructed using the mentioned databases from 1950 to 2011 for nine locations in the Iberian Peninsula. The monthly TOC climatology in the nine locations is presented. An exhaustive analysis is performed of TOC series trends and their statistical significance in the periods 1950-2011, 1950-1984, and 1985-2011. A significant ozone reduction between 1950 and 2011 appears in the Iberian Peninsula with a strong reduction from the late 1970s to the mid-1990s and with more or less constant or slightly increasing levels in the last 17 year. These trends are recalculated taking into account of uncertainty in the TOC values of the series, with a decrease in the number of statistically significant trends emerging. The statistically significant trends in annual and in the averaged Iberian Peninsula series are usually still significant even considering the uncertainty. Finally, a study is carried out of the uncertainty caused by TOC uncertainty in total shortwave and erythemal ultraviolet irradiances simulated under cloudless skies using a radiative transfer model.

Erythemal ultraviolet irradiation trends in the Iberian Peninsula from 1950 to 2011

“…TOC evolution in the Iberian Peninsula was studied in depth by Román et al (2014d) in the dimming and brightening periods, with usually negative but not statistically significant trends being reported in both periods, and a statistically significant trend of −0.7 % dc −1 (percent per decade units) in the annual TOC between 1950 and 2011. Antón and Mateos (2013) showed that these TOC changes have no significant influence on SW radiation (e.g.…”

“…Recently, Román et al (2014d) obtained the TOC trends from 1950 to 2011 on the Iberian Peninsula, and Román et al (2014a) the SW and temperature trends for the same period and region, but not the UVER trends due to the lack of UVER data. As a first step, Román et al (2014b) simulated the UVER irradiance under cloudless conditions on the Iberian Peninsula with a radiative transfer model, using as inputs monthly climatological values of aerosols, water vapour, etc.…”

“…These series comprised different databases: groundbased ozone; ozone retrieved from the TOMS (Total Ozone Mapping Spectrometer) instrument on board the Nimbus-7, Meteor-3, and Earth-probe satellites; TOC from OMI; retrieved TOC from the GOME (Global Ozone Monitoring Experiment) and GOME-2 instruments on board the ERS-2 and MetOp-A satellites; and reconstructed ozone data from the COST-726 project (Krzyscin, 2008;www.cost726.org). The construction of these TOC series was explained by Román et al (2014d), who, by means of an intercomparison with ground measurements, calculated that the combined uncertainty of the daily TOC values of these series was around 10 Dobson units (DU).…”

“…In addition, daily surface albedo at 360 nm between 1957 and 2002 was obtained from the COST-726 project database as an interpolation at each location of the available data grid (Schwander et al, 1999;Tanskanen, 2004). More information concerning the albedo and ozone data used in this work is available in Román et al (2014d).…”

“…The daily TOC at each location was included in the inputs, changing the value for each location on each day. Finally, the surface albedo values were also monthly averaged for each wavelength (twelve monthly values at each location for each available wavelength), these monthly values being linearly interpolated to obtain the monthly surface albedo at all the other wavelengths to be then used as input in the radiative transfer code (it is well detailed in Román et al, 2014d).…”