Analysis of the seasonal ozone budget and the impact of the summer monsoon on the northeastern Qinghai‐Tibetan Plateau

Abstract

AbstractSeasonal variations in ozone (O3) and the impact of the East Asian summer monsoon at Mount Waliguan (WLG) in the northeastern Qinghai‐Tibetan Plateau (TP) and in the surrounding regions were analyzed for 1997–2007 using a global chemical transport model coupled with O3 tagging simulations. The model‐simulated O3 and its precursors agreed well with observed values. An O3 budget analysis combined with O3 tagging results implied that photochemistry over the TP and long‐range transport of O3 from East Asia, Europe, and Africa were responsible for the surface O3 summer maximum at WLG. In June, the contribution of O3 from the TP was 11.8 ppbv, and the total contribution of O3 transport from eastern China, Japan, Korean Peninsula, Europe, and Africa was 22.7 ppbv. At 400 mb, the O3 exports from the stratosphere, Europe, Africa, and the Americas seemed to be the main sources of O3 at WLG. The contributions to surface O3 from deep convection process and lightning‐induced photochemistry at WLG were both low in summer and are unlikely to be the key processes or contributors for the O3 peak. At several mountain sites in southeast East Asia, the increasing summer monsoon index was related to a decreasing trend for O3 from spring onward at Mount Tai and Mount Huang. At Mount Hua and WLG, regional O3 accumulated over the monsoon's northernmost marginal zone under the influence of the East Asian summer monsoon and TP thermal circulation; this is most likely a key reason for the O3 summer maxima.