Assessment of Tropical Atlantic ocean variability and associated rainfall sensibility due to atmospheric ozone changes

Considering the impacts of atmospheric ozone changes on climate, its effects on Tropical Atlantic Variability (TAV) since 1955 are investigated. Two ensembles of simulations from the Community Earth System Model Large Ensemble Project are examined. One of them (varO(3)) considers historic tropospheric and stratospheric ozone levels while the other (fixO(3)) keeps ozone fixed at the 1955 levels. Results for varO(3) reveal a warming in the northern Tropical Atlantic (TA) when compared to fixO(3), which is more pronounced in boreal spring, and a cooling of the southern TA in early summer. A dipole-like pattern was also observed in the mean zonal wind stress field, with a weakening of the trade winds in northern TA and strengthening in southern TA, although the strongest difference is observed in the southern westerlies, which are intensified. As for the impact on the main rainfall regions, results show differences between the experiments in the depiction of the Atlantic Ocean convergence zones. The fixed ozone experiment shifts the ITCZ position to the south, which leads to an increase in precipitation over most of Northeast Brazil and western South Africa, in addition to simulating lower pre-cipitation in the South Atlantic Convergence Zone region. However, although there are differences in SST and precipitation between varO(3) and fixO(3), the ozone influence on TAV is not significant.