Stratospheric ozone depletion: a key driver of recent precipitation trends in South Eastern South America

Abstract

On a hemispheric scale, it is now well established that stratospheric ozone depletion has been the principal driver of externally forced atmospheric circulation changes south of the Equator in the last decades of the 20th Century. The impact of ozone depletion has been felt over the entire hemisphere, as reflected in the poleward drift of the midlatitude jet, the southward expansion of the summertime Hadley cell and accompanying precipitation trends deep into the subtropics. On a regional scale, however, surface impacts directly attributable to ozone depletion have yet to be identified. In this paper we focus on South Eastern South America (SESA), a region that has exhibited one of the largest wetting trends during the 20th Century. We study the impact of ozone depletion on SESA precipitation using output from 6 different climate models, spanning a wide range of complexity. In all cases we contrast pairs of model integrations with and without ozone depletion, but with all other forcings identically specified. This allows for unambiguous attribution of the computed precipitation trends. All 6 climate models consistently reveal that stratospheric ozone depletion results in a significant wetting of SESA over the period 1960-1999. Taken as a whole, these model results strongly suggest that the impact of ozone depletion on SESA precipitation has been as large as, and quite possibly larger than, the one caused by increasing greenhouse gases over the same period.

Influences of the Antarctic Ozone Hole on Southern Hemispheric Summer Climate Change

“…Several previous studies have linked both interannual and longer decadal variations in the SAM to temperature changes elsewhere in the SH (Thompson and Solomon 2002;Gillett and Thompson 2003;Gillett et al 2006;Manatsa et al 2013) and with cooler conditions in the summer over much of eastern Australia (Hendon et al 2007;Meneghini 2007). More recent modeling and observational studies have shown that ozone depletion can affect both mean and extreme rainfall in the southern subtropics, with enhanced precipitation in Australia and South America in the austral summer (Kang et al 2011;Fyfe et al 2012;Kang et al 2013;Gonzalez et al 2014). The positive SAM trend reflects a poleward shift of the extratropical jet and accompanying storm tracks (Archer and Caldeira 2008) and a poleward shift of the edge of the Hadley cell (Hu and Fu 2007).…”

Zonally asymmetric trends of winter total column ozone in the northern middle latitudes

“…Kirchner and Peters 2003;Peters et al 2015) compared to zonally symmetric ozone variations. In many long-term General Circulation Model simulations, a prescribed time series of zonal mean ozone is employed (Cagnazzo et al 2006;Cionni et al 2011;Szopa et al 2013;Gonzalez et al 2014;Xie et al 2016Xie et al , 2017 and the ZAO heating effects, which have an important contribution to chemical-radiative-dynamical feedbacks (e.g. Sassi et al 2005;Nathan and Cordero 2007;Gabriel et al 2007Gabriel et al , 2013McCormack et al 2011;Peters et al 2015), are not properly considered.…”

The Antarctic ozone hole during 2012

“…Over the past few decades, the most significant changes in southern hemisphere climate have included [Canziani et al, 2014]: (1) a southward shift and intensification of the tropospheric eastward jet over the Southern Ocean region-resulting in a tendency for the extratropical storm tracks to move poleward; (2) anomalously dry conditions have occurred over southern Australia, New Zealand and southern South America, and anomalously wet conditions over northwestern Australia and South Africa; (3) a warming of the Southern Ocean and its waters have become less saline; (4) a warming of the Antarctic Peninsula and its oceanic margins; (5) an expansion the tropical zone and a shift of atmospheric mass from mid to higher latitudes (Hendon et al, 2007;Calvo et al, 2012;Gonzalez et al, 2013;Turner et al, 2013);and (6) an increase in Antarctic average sea-ice extent. These changes are largely consistent with industrial era effects expected from increasing levels of anthropogenic greenhouse gases and the more recent effects caused by ozone depletion, and are largely though not exclusively related to observed changes in the meridional location of the mid-latitude tropospheric jet during recent decades (Lin et al, 2009;Fu et al, 2010).…”