Impact of chemical production and transport on summertime diurnal ozone behavior at a mountainous site in North China plain

Abstract

The impact of chemical production and transport on diurnal ozone behavior in June 2006 at a mountainous site (Mt. Tai) in North China Plain (NCP) was studied by regional chemical transport coupled with a process analysis and a tagged tracer method. The observed diurnal variation in the morning minimum-afternoon maximum was reproduced well. The results showed that regional transport contributed ~60 ppbv to "background" ozone, with no significant diurnal variations (< 7 ppbv), while the chemistry (~25 ppbv) in the surrounding region (an area of 150,000 km2) which demonstrated an afternoon-maximum explained the causes of diurnal ozone behavior. The process analysis also suggested that in-situ chemistry accounted for most of the increase in ozone from morning to mid-afternoon (rather than the ozone concentration itself), with a minor contribution from vertical transport. A comparison was conducted between Mt. Tai and a mountainous site in Japan (Happo) to determine the regional variability in photochemistry and transport over Eastern Asia. The results showed that photochemical activities around Mt. Tai were stronger than those around Happo, where dynamic processes, rather than in-situ chemistry, played a dominant role in the diurnal behavior of ozone at midnight (0:00-3:00 local time (LT) and at the maximaminima before noon (11:00 LT).