Impacts of Uncertainty in AVOC Emissions on the Summer ROx Budget and Ozone Production Rate in the Three Most Rapidly-Developing Economic Growth Regions of China

High levels of uncertainty in non-methane volatile organic compound （NMVOC） emissions in China could lead to significant variation in the budget of the sum of hydroxyl （OH） and peroxy （HO2,RO2） radicals （ROx =OH ＋ HO2 ＋ RO2） and the ozone production rate [P（O3）],but few studies have investigated this possibility,particularly with three-dimensional air quality models.We added diagnostic variables into the WRF-Chem model to assess the impact of the uncertainty in anthropogenic NMVOC （AVOC） emissions on the ROx budget and P（O3） in the Beijing-Tianjin-Hebei region,Yangtze River Delta,and Pearl River Delta of China.The WRF-Chem simulations were compared with satellite and ground observations,and previous observation-based model studies.Results indicated that 68％ increases （decreases） in AVOC emissions produced 4％-280％ increases （2％-80％ decreases） in the concentrations of OH,HO2,and RO2 in the three regions,and resulted in 35％-48％ enhancements （26％-39％ reductions） in the primary ROx production and ～ 65％ decreases （68％-73％ increases） of the P（O3） in Beijing,Shanghai,and Guangzhou.For the three cities,the two largest contributors to the ROx production rate were the reaction of O1D ＋ H2O and photolysis of HCHO,ALD2,and others; the reaction of OH ＋ NO2 （71％-85％） was the major ROx sink; and the major contributor to P（O3） was the reaction of HO2 ＋ NO （～ 65％）.Our results showed that AVOC emissions in 2006 from Zhang et al.（2009） have been underestimated by ～ 68％ in suburban areas and by ＞ 68％ in urban areas,implying that daily and hourly concentrations of secondary organic aerosols and inorganic aerosols could be substantially underestimated,and cloud condensation nuclei could be underestimated,whereas local and regional radiation was overestimated.