Abstract
Abstract. A 3-D regional chemical transport model, the Nested Air Quality Prediction Model System (NAQPMS), with an on-line tracer tagging module was used to study the source of the near-ground (<1.5 km above ground level) ozone at Mt. Tai (36.25° N, 117.10° E, 1534 m a.s.l.) in Central Eastern China (CEC) during the Mount Tai eXperiment 2006 (MTX2006). The model reproduced the temporal and spatial variations of near-ground ozone and other pollutants, and it captured highly polluted and clean cases well. The simulated near-ground ozone level over CEC was 60–85 ppbv (parts per billion by volume), which was higher than values in Japan and over the North Pacific (20–50 ppbv). The simulated tagged tracer data indicated that the regional-scale transport of chemically produced ozone over other areas in CEC contributed to the greatest fraction (49%) of the near-ground mean ozone at Mt. Tai in June; in situ photochemistry contributed only 12%. Due to high anthropogenic and biomass burning emissions that occurred in the southern part of the CEC, the contribution to ground ozone levels from this area played the most important role (32.4 ppbv, 37.9% of total ozone) in the monthly mean ozone concentration at Mt. Tai; values reached 59 ppbv (62%) on 6–7 June 2006. The monthly mean horizontal distribution of chemically produced ozone from various ozone production regions indicated that photochemical reactions controlled the spatial distribution of O3 over CEC. The regional-scale transport of pollutants also played an important role in the spatial and temporal distribution of ozone over CEC. Chemically produced ozone from the southern part of the study region can be transported northeastwardly to the northern rim of CEC; the mean contribution was 5–10 ppbv, and it reached 25 ppbv during high ozone events. Studies of the outflow of CEC ozone and its precursors, as well as their influences and contributions to the ozone level over adjacent regions/countries, revealed that the contribution of CEC ozone to mean ozone mixing ratios over the Korean Peninsula and Japan was 5–15 ppbv, of which about half was due to the direct transport of ozone from CEC and half was produced locally by ozone precursors transported from CEC.
Highlights
The importance of tropospheric ozone (O3) on air quality, atmospheric chemistry, and climate change has been recognized over the last several decades (Brasseur et al, 1999; IPCC, 2001)
Along with rapid urbanization and industrialization processes, the emissions of O3 precursors have significantly increased in China; this is in contrast to a significant decrease in Europe and little change in North America and Japan (Naja and Akimoto, 2004; Streets and Waldhoff, 2000)
To better describe the interactions between different regions in Central Eastern China (CEC), we provide the results for each region in CEC and treat the other ozone production regions as the outer region (Outer, which includes SIB, NWCHN, SWCHN, SCHN, ECHN, NECHN, PAC, KOR, JPN, and SEASA)
Summary
The importance of tropospheric ozone (O3) on air quality, atmospheric chemistry, and climate change has been recognized over the last several decades (Brasseur et al, 1999; IPCC, 2001). Along with rapid urbanization and industrialization processes, the emissions of O3 precursors have significantly increased in China; this is in contrast to a significant decrease in Europe and little change in North America and Japan (Naja and Akimoto, 2004; Streets and Waldhoff, 2000). Central Eastern China (CEC, 30◦ N–40◦ N, 110◦ E–130◦ E) is the biggest emitter of anthropogenic trace gases and aerosols in China (NOx emissions reached 3600 Gg/a in 2000, which was 32% of the total emissions in China) (Streets and Waldhoff, 2000). CEC exhibited a continuous and marked increase in tropospheric NO2 column densities during the period 1996–2004 (Akimoto et al, 2006; Richter et al, 2005).
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