Chemistry and dynamics of tropospheric ozone in the background atmosphere of the Qinghai-Tibet Highland

Tropospheric ozone in remote regions of the Northern Hemisphere typically shows maximum in spring, however it peaks in summer northeastern part (Mt Wualiguan (WLG) Global Baseline Station) of the Qinghai-Tibet Plateau in western China. To find out reasons, we conducted two field measurements and modeling studies. The results show that (1) local NOx concentrations are high enough to sustain net formation of ozone summer; (2) downward transport of ozone from the stratosphere and the horizontal transport from developed eastern China contributed to surface ozone at WLG.

Figure 1. Average diurnal patterns of O3, CO, NO, NOy, and surface winds at WLG for (a) spring and (b) summer, error bars indicate standard errors.

Figure 2. Modeled O3 in situ productions, destruction, and net rates at WLG in (a)spring and (b) summer

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Figure 3. (a) the 340K IPV map and back trajectories ending at 2-6 km over WLG at 1200 UTC 18 June, and (b) cross section of PV, wind speed and clear-air-turbulence on 100.9 E at 1200 UTC 18 June.

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