Nanjing University, China
Title: Ozone pollution and its link with heat wave and East Asia Summer Monsoon
Tijian Wang is a professor and vice director of School of Atmospheric Science of Nanjing University, committee member of IGAC-China, Deputy Secretary-General of Atmospheric Environmental Society of Chinese Environmental Science Society and vice director of Atmospheric Composition Society Chinese of Meteorological Society. His research interests center around regional air pollution and climate change, urban atmospheric chemistry and environmental meteorology, air quality and haze weather forecast, atmospheric deposition and air-soil exchange. More than 200 papers have been published in the domestic and international professional journals.
Ozone plays a key role in global and regional climate change and atmospheric environment. Tropospheric ozone is not only a main greenhouse gas, but also a secondary pollutant. In East Asia，ozone can be affected both in concentration and spatial pattern by typical monsoon climate and high ozone is always linked with heat wave. Using regional climate model RegCM-Chem, the difference of ozone between strong monsoon years and weak monsoon years was analyzed. It was found that EASM intensity can significantly influence the spatial distribution of the low-level ozone. When EASM is strong, ozone in central Asia (28°N ~ 42° N) was reduced, but inversed in the north and south. Surface ozone difference range from -6.5 to 6.9ppb during the four months(May to August) in summer monsoon season, showing the most obvious difference in August. Difference of four month averaged ozone range from -3 to 3.8 ppb and regional variation range from-10% to 25%. Process analysis shows that the main factors controlling ozone level during summer monsoon seasons are the advection and chemistry. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41.1 °C, 6.1 °C higher than the definition of heat wave in China, and can last for as long as 27 days. Maximum ozone reached 160.5 ppb, exceeding the national air quality standard (secondary level) as 74.7 ppb. Moreover, ozone was found to increase at a rate of 4-5 ppb K-1 within the temperature range of 28-38 °C, but decrease by a rate of -1.3~-1.7 ppb K-1 under extremely high temperature. Modeling studies show that chemical reactions play the most important role in ozone formation during heat wave days. High temperature also slightly promote the effect of dry deposition velocity, vertical turbulence and horizontal advection, which beneficial to ozone remove, but the magnitude is much smaller than chemical effect.