Analysis of seasonal ozone budget and spring ozone latitudinal gradient variation in the boundary layer of the Asia-Pacific region

The ozone (O3) budget in the boundary layer of the Asia-Pacific region (AP) was studied from 2001 to 2007 using the output of Model of Ozone and Related chemical Tracers, version 4 (MOZART-4). The model-simulated O3 data agree well with observed values. O3 budget analysis using the model output confirms that the dominant factor controlling seasonal variation of O3 differs by region. Photochemistry was found to play a critical role over Japan, the Korean Peninsula and Eastern China. Over the northwestern Pacific Ocean, advective flux was found to drive the seasonal variation of O3 concentrations. The large latitudinal gradient in O3 with a maximum of 52 ppbv over the marine boundary layer around 35°N during the spring was mainly due to chemistry; meanwhile, advection was found to weaken the gradient. The contribution of stratospheric O3 was ranked second (20%) to the local contribution (25%) in Japan and the Korean Peninsula near 35°N. The rate of O3 export from Chinaʹs boundary layer was the highest (approximately 30%) in low latitudes and decreased with increasing latitude, while the contribution of North America and Europe increased with increasing latitude, from 10% in lower latitudes to 24% in higher latitudes.