The Change Of Atmospheric Ozone And Nitrogen Dioxide And Their Driving Forces

Seasonal patterns and annual variations of ozone in the planetary boundary layer are analyzed using the observational data over Western Pacific during2000-2010. The data sets include ozone sounding data at Hong Kong, Sapporo and Naha, satellite retrieval tropospheric excess columns of NO2, surface ozone and meteorological variables. The results show very different seasonal patterns of ozone at the three sites. Both Hong Kong and Naha show bimodal patterns with peak values in spring and autumn and the lowest value in summer, whereas Sapporo has one peak in spring. Meteorological conditions and human activities account for such difference in seasonal patterns. Similar increase rates of ozone (0.80versus0.77ppb/year) are found within the planetary boundary layer at both Naha and Sapporo sites. Hong Kong shows the smallest annual change but the largest increase rate (1.21ppb/year) in autumn. The tropospheric columns NO2retrieved from GOME and SCIAMACHY measurements indicate that the increasing O3within the planetary boundary layer at Sapporo, Naha (annual mean) and Hong Kong (seasonal mean in autumn) are resulting from the increasing anthropogenic emissions and regional transport. The cluster analyses of backward trajectories calculated with HYSPLIT confirm further that the increases in O3over Naha and Sapporo are attributed to the regional transport from Northeastern China.China has been undergoing rapid urbanization transformation over the past several decades.The uban built-up areas (population) were (was) increased by275%(110%),440%(93%), and707%(50%) in Beijing, Shanghai and Guangzhou, respectively from1985to2010(201l).The satellite retrieval data are used to quantify the impact of rapid urbanization on seasonal changes in tropospheric nitrogen dioxide (NO2) over East China. The results show that rapid urbanization has profound effect on tropospheric column of NO2. During1996-2011, the linear regression shows the yearly growth rates of tropospheric NO2column amount were increased by18%,17%,18%, and22%in spring, summer, autumn, and winter, respectively over the Yangze River Delta (YRD), and20%,11%,19%, and21%over the Bohai Economic Rim (BER). The corresponding seasonal changes over PRD were6%,9%,10%, and7%. There was reduction of tropospheric NO2by15%over the BER and by12%over the YRD in autumn2008, at the time of the Beijing2008Olympic Games, relative to the same season in2007. However, after the Games, the decreasing trend was reversed and the increase was even faster than before. Our results show that the increase in tropospheric NO2column amount occurred over the three regions at rates1.3-8times faster than a recent inventory estimateof NOx emissions for2000-2010. We also discuss the impact of urbanization on tropospheric ozone and found that OMI retrievals tropospheric ozone column show relatively smaller sensitivity to urbanization and the changes in tropospheric NO2.