Summer ozone variation in North China based on satellite and site observations

Abstract. Compared with other regions, air pollution in North China is very serious, especially its levels of fine particulate matter, which are closely associated with the concentrations of polluting gases, such as nitrogen oxides, sulfur oxides, organic gases, and ozone. Fine particle pollution has been studied in-depth, but there is less known about ozone. This paper focuses on the interannual variability of tropospheric ozone in North China and identifies its influential factors. Our analysis relies on satellite observations (ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide and formaldehyde concentrations) and near-surface data (carbon monoxide, sulfur dioxide, nitrogen dioxide, fine particulate concentrations, temperature, and humidity). Studies have shown that the tropospheric ozone column in North China has been at a high level for the past 3 years, with the similar time series for temperature and formaldehyde. However, trends in ozone are opposite to those of sulfur dioxide and nitrogen dioxide over this 3-year period. This indicates that the increase in ozone in North China was mainly caused by the increase in temperature and an increase in organic gas content, rather than by nitrogen oxides. Over both temporal and spatial scales, the production rate of ozone appears to be most sensitive to temperature change, as ground observations in Beijing have suggested.