On the possible causes of recent increases in northern hemispheric total ozone from a statistical analysis of satellite data from 1979 to 2003

Abstract

Abstract. Global total ozone measurements from various satellite instruments such as SBUV, TOMS, and GOME show an increase in zonal mean total ozone at northern hemispheric (NH) mid to high latitudes since the mid-nineties. This increase could be expected from the peaking and start of decline in the effective stratospheric halogen loading, but the rather rapid increase observed in NH zonal mean total ozone suggests that another physical mechanism such as winter planetary wave activity has increased which has led to higher stratospheric Arctic temperatures. This has enhanced ozone transport into higher latitudes in recent years as part of the residual circulation and at the same time reduced the frequency of cold Arctic winters with enhanced polar ozone loss. Results from various multi-variate linear regression analyses using SBUV V8 total ozone with explanatory variables such as a linear trend or, alternatively, EESC (equivalent effective stratospheric chlorine) and on the other hand planetary wave driving (eddy heat flux) or, alternatively, polar ozone loss (PSC volume) in addition to proxies for stratospheric aerosol loading, QBO, and solar cycle, all considered to be main drivers for ozone variability, are presented. It is shown that the main contribution to the recent increase in NH total ozone is from the combined effect of rising tropospheric driven planetary wave activity associated with reduced polar ozone loss at high latitudes as well as increasing solar activity. This conclusion can be drawn regardless of the use of linear trend or EESC terms in our statistical model. It is also clear that more years of data will be needed to further improve our estimates of the relative contributions of the individual processes to decadal ozone variability. The question remains if the observed increase in planetary wave driving is Correspondence to: S. Dhomse (sandip@iup.physik.uni-bremen.de) part of natural decadal atmospheric variability or will persist. If the latter is the case, it could be interpreted as a possible signature of climate change.

Evaluation of the inter-annual variability of stratospheric chemical composition in chemistry-climate models using ground-based multi species time series

“…On each figure, the left-hand plot refers to the raw data time series (total variance) and the middle plot refers to the deseasonalized time series. In order to deseasonalize the time series, the mean seasonal cycle, defined as monthly means averaged over the corresponding months of the time series, is subtracted from the raw time series (Ziemke et al, 1997, Staehelin et al 2001, Dhomse et al, 2006. The robustness of this deseasonalisation method has been tested by comparing the results with another widely applied deseasonalisation method using multiple harmonics as a functional for the seasonal cycle (Stolarski et al, 1991, Brunner et al, 2006, CCMVal, 2010.…”

“…As a result, a large part of the interannually generated variability, at least the internal component, cannot in any way be accounted for by our MLR analysis. Note that, in some studies of polar ozone variability, the MLR also includes atmospheric parameters such as temperature or heat fluxes into the stratosphere as explanatory variables (Svendby et al, 2004;Brunner et al, 2006;Dhomse et al, 2006;Wohltmann et al, 2007;Harris et al, 2008). In that way, some internal variability can be accounted for in the MLR.…”

Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

“…This circulation plays a crucial role in determining the evolution of the background as well as volcanically enhanced stratospheric aerosol layer. Stronger BD circulation leads to more rapid transport of air masses (and chemical species) from the tropics to high latitudes (e.g, Weber et al 2003;Dhomse et al 2006). This circulation also affects aerosol removal from the stratosphere (e.g.…”

SOLAR VARIABILITY FROM 240 TO 1750 nm IN TERMS OF FACULAE BRIGHTENING AND SUNSPOT DARKENING FROM SCIAMACHY

“…Among various periodicities, the 11 year solar cycle is the most pronounced to affect current terrestrial stratospheric ozone trends (Dhomse et al 2006;Steinbrecht et al 2004Steinbrecht et al , 2006. Different satellite platforms have established variations of total solar irradiance, (TSI or "solar constant") to vary between 0.003% and 0.015% in minutes, 0.2% in months, and 0.1% over decades (Lang 2006;Fröhlich & Lean 2004;Foukal 2004;Hufbauer 1991).…”