Articles | Volume 17, issue 18
Atmos. Chem. Phys., 17, 11293–11311, 2017

Special issue: Study of ozone, aerosols and radiation over the Tibetan Plateau...

Atmos. Chem. Phys., 17, 11293–11311, 2017

Research article 25 Sep 2017

Research article | 25 Sep 2017

Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

Xiufeng Yin1,2,3, Shichang Kang1,3,4, Benjamin de Foy5, Zhiyuan Cong2,4, Jiali Luo6, Lang Zhang2, Yaoming Ma2,3,4, Guoshuai Zhang2, Dipesh Rupakheti2,3, and Qianggong Zhang2,4 Xiufeng Yin et al.
  • 1State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, 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

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 continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of  ∼ 5 years (January 2011 to October 2015), which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation) 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 inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau. This work may provide a reference for future model simulations.

Short summary
We presented 5-year surface ozone measurements at Nam Co in the inland Tibetan Plateau and made a synthesis comparison of diurnal and seasonal patterns on regional and hemispheric scales. Surface ozone at Nam Co is mainly dominated by natural processes and is less influenced by stratospheric intrusions and human activities than on the rim of the Tibetan Plateau. Ozone at Nam Co is representative of background that is valuable for studying ozone-related effects on large scales.
Final-revised paper