Updated Simulation of Tropospheric Ozone and Its Radiative Forcing over the Globe and China Based on a Newly Developed Chemistry–Climate Model

This study evaluates the performance of a newly developed atmospheric chemistry–climate model, BCCAGCM＿CUACE2.0（Beijing Climate Center Atmospheric General Circulation Model＿China Meteorological Administration Unified Atmospheric Chemistry Environment） model, for determining past（2010） and future（2050） tropospheric ozone（O3） levels. The radiative forcing（RF）, effective radiative forcing（ERF）, and rapid adjustments（RAs,both atmospheric and cloud） due to changes in tropospheric O3 are then simulated by using the model. The results show that the model reproduces the tropospheric O3 distribution and the seasonal changes in O3 surface concentration in 2010 reasonably compared with site observations throughout China. The global annual mean burden of tropospheric O3 is simulated to have increased by 14.1 DU in 2010 relative to pre-industrial time, particularly in the Northern Hemisphere. Over the same period, tropospheric O3 burden has increased by 21.1 DU in China, with the largest increase occurring over Southeast China. Although the simulated tropospheric O3 burden exhibits a declining trend in global mean in the future, it increases over South Asia and Africa, according to the Representative Concentration Pathway（RCP） 4.5 and 8.5 scenarios. The global annual mean ERF of tropospheric O3 is estimated to be 0.25 W m-2in 1850-2010, and it is 0.50 W m-2 over China. The corresponding atmospheric and cloud RAs caused by the increase of tropospheric O3 are estimated to be 0.02 and 0.03 W m-2, respectively. Under the RCP2.6, RCP4.5,RCP6.0, and RCP8.5 scenarios, the annual mean tropospheric O3 ERFs are projected to be 0.29（0.24）, 0.18（0.32）,0.23（0.32）, and 0.25（0.01） W m-2 over the globe（China）, respectively.