Characteristics of vertical ozone distribution and ozone transport in the troposphere over Hong Kong

This thesis intends to study the characteristics of vertical ozone (O 3) distribution and O3 transport in the troposphere over Hong Kong with an aim to identify the major sources of O3 in the subtropical atmosphere.;The O3 distributions are studied through a total of 172 ozonesonde soundings and 3-year O3 and carbon monoxide (CO) measurements from a background monitoring station in Cape D' Aguilar, Hok Tsui. The effects of O3 change on climate in South China region are assessed through empirical formulation and field data.;Tropospheric O3 shows a strong seasonal cycle with a maximum in spring and a minimum in summer. It also has periodic low value in the upper troposphere in autumn and winter. The winter and spring seasons are transition periods with a minor peak in spring.;The biomass burning emissions associated with the active fires in Southeast Asia (SE Asia) continent are found to cause substantial O3 enhancements in the lower troposphere in springtime over Hong Kong.;Widespread tropospheric O3 enhancement was observed over Hong Kong and most tropical and subtropical western Pacific in 1997 when huge amount of biomass was burned in the forest fire in Indonesia. The fires and O 3 build-up were directly related to the unexceptionally drought conditions and abnormal tropospheric environment associated with the strong El Nino phenomenon.;Low O3 concentration was commonly observed in the upper troposphere during autumn and winter over Hong Kong. Aircraft measurement reveals that such low O3 is large-scale in nature and is also found in the upper troposphere of the whole of tropical and subtropical western Pacific.;In the surface layer, background O3 and CO show a strong and non-linear relationship throughout spring, summer and autumn. The import of O3 in the prevalent air mass accompanying the long-range transport process associated with the East Asian monsoon and climate system is the dominant factor governing its fluctuation in South China. (Abstract shortened by UMI.).