Abstract
Abstract. Climate models that do not simulate changes in stratospheric ozone concentrations require the prescription of ozone fields to accurately calculate UV fluxes and stratospheric heating rates. In this study, three different global ozone time series that are available for this purpose are compared: the data set of Randel and Wu (2007) (RW07), Cionni et al. (2011) (SPARC), and Bodeker et al. (2013) (BDBP). All three data sets represent multiple-linear regression fits to vertically resolved ozone observations, resulting in a spatially and temporally continuous stratospheric ozone field covering at least the period from 1979 to 2005. The main differences among the data sets result from regression models, which use different observations and include different basis functions. The data sets are compared against ozonesonde and satellite observations to assess how the data sets represent concentrations, trends and interannual variability. In the Southern Hemisphere polar region, RW07 and SPARC underestimate the ozone depletion in spring ozonesonde measurements. A piecewise linear trend regression is performed to estimate the 1979–1996 ozone decrease globally, covering a period of extreme depletion in most regions. BDBP overestimates Arctic and tropical ozone depletion over this period relative to the available measurements, whereas the depletion is underestimated in RW07 and SPARC. While the three data sets yield ozone concentrations that are within a range of different observations, there is a large spread in their respective ozone trends. One consequence of this is differences of almost a factor of four in the calculated stratospheric ozone radiative forcing between the data sets (RW07: −0.038 Wm−2, SPARC: −0.033 Wm−2, BDBP: −0.119 Wm−2), important in assessing the contribution of stratospheric ozone depletion to the total anthropogenic radiative forcing.
Highlights
The differences in radiative forcing between the ozone data sets imply different surface climate responses when the ozone data sets are used in climate models; further, the larger ozone decreases at mid- and high latitudes in the BDBP data set can be expected to cause larger responses of climatic modes of variability compared with RW07 and Stratospheric Processes and their Role in Climate (SPARC) data sets
All three data sets are based on regression model output, and the degree of variability described by them depends strongly on the number and the choice of basis functions used for their creation
The overall pattern of the climatologies look very similar for all three data sets, and compare well to TOMS/SBUV data and the FK98 climatology
Summary
UdissitnrigbuatiorenaalinsdtMicitsorecdphraeenslegneDtsaeotivovener otliofmptehmeinseatracnthotasnpghienrgiccloimzoantee is important for quantifying the flux of harmful UV radiation from the sun reaching the earth’s surface, and to understand changes inHthyeddryonalomgicys aandnednergy budget of tohzeoneaerdthe’psleattimonosipnhgelroeb.aClEacpliatmurraittnhegmtShoedyeoslbstseiesrmvcreudcsiatrlaftoorsprehperroicducing stratospheric temperatureSchcainegnesc(eDasll’Amico et al., 2010), Southern Hemisphere (SH) tropospheric circulation changes (Son et al, 2009; Polvani et al, 2011), climate and surface temperatures in Antarctica (Gillett and Thompson, 2003), et al, global 2009). This study focuses on three ozone data sets that (i) have high vertical resolution, (ii) cover the entire globe throughout the period from at least 1979–2005, and (iii) have been mainly created to provide climate models with a realistic ozone input. We discuss trends in the data sets, focussing on the ozone change from 1979 to 1996, a period of extreme depletion in many regions The purpose of this is to assess the extent to which the data sets capture the observed ozone decreases, we emphasize that the data sets are not suitable for assessing the true ozone trend as they are all based on regression model output and any trends are effectively imposed by the fit to a linear trend or EESC basis function in the regression model.
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