Surface ozone at Nam Co (4730 m a.s.l.) in the inland Tibetan Plateau:
variation, synthesis comparison and regional representativeness
Xiufeng Yin1,2,3, Shichang Kang1,4, Benjamin de Foy5, Zhiyuan Cong2,4, Jiali Luo6, Lang Zhang2, Yaoming Ma2,4, Guoshuai Zhang2, Dipesh Rupakheti2,3, and Qianggong Zhang2,41State Key Laboratory of Cryosphere Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Science, Lanzhou, 730000, China 2Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China 3University of Chinese Academy of Sciences, Beijing, 100039, China 4CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100085, China 5Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO, 63108, USA 6Key Laboratory of Semi-Arid Climate Change, Ministry of Education, Lanzhou, 730000, China
Received: 26 Feb 2017 – Accepted for review: 24 Mar 2017 – Discussion started: 27 Mar 2017
Abstract. Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present long-term measurements for ~ 5 years (January 2011 to October 2015) of surface ozone mixing ratios at Nam Co Station, which is a regional background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions and potential local vertical mixing. Model results indicate that the study site is affected by the surrounding areas in different seasons and that air masses from the northern Tibetan Plateau lead to increased ozone levels in the summer. In contrast to the surface ozone levels at the edges of the Tibetan Plateau, those at Nam Co Station are less affected by stratospheric intrusions and human activities which makes Nam Co Station representative of vast background areas in the central Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites in the Tibetan Plateau and beyond, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau. This work may provide a reference for model simulations in the future.
Yin, X., Kang, S., de Foy, B., Cong, Z., Luo, J., Zhang, L., Ma, Y., Zhang, G., Rupakheti, D., and Zhang, Q.: Surface ozone at Nam Co (4730 m a.s.l.) in the inland Tibetan Plateau:
variation, synthesis comparison and regional representativeness, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-175, in review, 2017.