Natural emissions under future climate condition and their effects on surface ozone in the Yangtze River Delta region, China

Abstract The natural emissions of ozone precursors (NO x and VOCs) are sensitive to climate. Future climate change can impact O 3 concentrations by perturbing these emissions. To better estimate the variation of natural emissions under different climate conditions and understand its effect on surface O 3 , we model the present and the future air quality over the Yangtze River Delta (YRD) region by running different simulations with the aid of the WRF-CALGRID model system that contains a natural emission module. Firstly, we estimate the natural emissions at present and in IPCC A1B scenario. The results show that biogenic VOC emission and soil NO x emission over YRD in 2008 is 657 Gg C and 19.1 Gg N, respectively. According to climate change, these emissions in 2050 will increase by 25.5% and 11.5%, respectively. Secondly, the effects of future natural emissions and meteorology on surface O 3 are investigated and compared. It is found that the variations in meteorological fields can significantly alter the spatial distribution of O 3 over YRD, with the increases of 5–15 ppb in the north and the decreases of −5 to −15 ppb in the south. However, only approximately 20% of the surface O 3 increases caused by climate change can be attributed to the natural emissions, with the highest increment up to 2.4 ppb. Finally, Ra (the ratio of impacts from NO x and VOCs on O 3 formation) and H 2 O 2 /HNO 3 (the ratio between the concentrations of H 2 O 2 and HNO 3 ) are applied to study the O 3 sensitivity in YRD. The results show that the transition value of H 2 O 2 /HNO 3 will turn from 0.3 to 0.5 in 2008 to 0.4–0.8 in 2050. O 3 formation in the YRD region will be insensitive to VOCs under future climate condition, implying more NO x need to be cut down. Our findings can help us understand O 3 variation trend and put forward the reasonable and effective pollution control policies in these famous polluted areas.