Simulation of the interannual variations of tropospheric ozone over China: Roles of variations in meteorological parameters and anthropogenic emissions

We quantify the interannual variations (IAVs) of tropospheric O-3 over China for the years 2004-2012 by using the one-way nested-grid version of the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem). The roles of variations in meteorological fields and anthropogenic emissions of O-3 precursors are examined separately and together through sensitivity simulations. With variations in both meteorological parameters and emissions, simulated seasonal mean surface-layer O-3 concentrations over North China (NC, 110-120 degrees E, 32-42 degrees N) exhibit the largest IAVs in June July August (JJA). The regionally averaged absolute percent departure from the mean (APDM) values over NC are 0.7%, 3.2%, 3.9%, and 2.1% in December January February (DJF), March April May (MAM), and September October November (SON), respectively. Over South China (SC, 110-120 degrees E, 22-32 degrees N), the IAVs of O-3 are found maximum in MAM, and minimum in JJA; the APDM values are 2.7%, 3.7%, 1.4%, and 2.6% in DJF, MAM, JJA, and SON, respectively. With respect to the IAVs of O-3 over the Sichuan Basin (SCB, 102-110 degrees E, 27-33 degrees N), the APDM values are simulated to be 2.7-3.8% throughout the year. The IAVs in surface-layer O-3 by variations in meteorological fields are simulated to be larger than those by variations in anthropogenic emissions throughout the year in NC and SC except for JJA in SC. The relatively more important role of variations in anthropogenic emissions is simulated in SCB in all seasons. Process analyses are performed to identify key meteorological parameters that influence the IAVs of O-3 over NC, SC, and SCB. Over all of these regions, variations in winds are found to have the largest impact on the IAVs of O-3, followed by those in temperature and specific humidity. Considering that the APDM values represent the IAVs averaged over 2004-2012, the magnitudes of IAVs of O-3 for specific years can be more significant than the numbers reported here. Our results have important implications for the effectiveness of short-term air quality control strategies in China. (C) 2015 The Authors. Published by Elsevier Ltd.