Abstract
Abstract. We have investigated the impact of the assumed nitrous oxide (N2O) increases on stratospheric chemistry and dynamics using a series of idealized simulations with a coupled chemistry-climate model (CCM). In a future cooler stratosphere the net yield of NOy from N2O is shown to decrease in a reference run following the IPCC A1B scenario, but NOy can still be significantly increased by extra increases of N2O over 2001–2050. Over the last decade of simulations, 50% increases in N2O result in a maximal 6% reduction in ozone mixing ratios in the middle stratosphere at around 10 hPa and an average 2% decrease in the total ozone column (TCO) compared with the control run. This enhanced destruction could cause an ozone decline in the first half of this century in the middle stratosphere around 10 hPa, while global TCO still shows an increase at the same time. The results from a multiple linear regression analysis and sensitivity simulations with different forcings show that the chemical effect of N2O increases dominates the N2O-induced ozone depletion in the stratosphere, while the dynamical and radiative effects of N2O increases are overall insignificant. The analysis of the results reveals that the ozone depleting potential of N2O varies with the time period and is influenced by the environmental conditions. For example, carbon dioxide (CO2) increases can strongly offset the ozone depletion effect of N2O.
Highlights
Stratospheric ozone destruction involves complex chemical reactions and a range of chemical species
The distribution of ozone changes resulting from N2O increases in a 3-D chemistry-climate model (CCM) was discussed and the chemical–dynamical–radiative feedbacks associated with N2Oincreases were analysed in this study
Subsequent climate changes induced by these N2O increases, such as changes in the stratospheric temperatures, the BD circulation and area of polar stratospheric clouds (PSCs), were examined
Summary
Stratospheric ozone destruction involves complex chemical reactions and a range of chemical species. Fleming et al (2011) further carried out a comprehensive study of longterm stratospheric effects of some source gases, including N2O and CO2, through a series of two-dimensional (2-D) chemistry-climate model simulations They predicted that in the latter half of the 21st century, CO2, N2O, and methane (CH4) loading will all have significant impacts on global total ozone, where the effect of CO2 changes on global total ozone has twice the magnitude of the effect of N2O changes. Other studies have shown that the effects of N2O on ozone depend on both the CO2 induced cooling and the chemical effects of CH4 (Portmann et al, 2012; Revell et al, 2012b) Those previous studies have investigated the impact of N2O on ozone depletion, the relative importance of the radiative and chemical effects of N2O remain unclear and the net effect of increased N2O on the ozone layer in a chang-.
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