The patterns of polar near-surface ozone associated with various atmospheric conditions
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Understanding the spatiotemporal pattern of near-surface ozone is the key part of polar atmospheric environment. The near-surface ozone can be depleted by the catalytic bromine chemistry in the heterogeneous phase but produced due to the snow photochemistry of nitrogen. In addition to the local chemistry, ozone pattern is also affected by regional meteorology and air-mass transport. Since the polar region is quite sensitive to the climate change, these conditions can be also affected by climate change and variability. Based on the analysis of large amount of dataset combined with in-situ observations, satellite measurements, model simulations, and global reanalysis data, the characteristics of polar ozone pattern and relation to the regional and large-scale atmospheric situations were investigated. At first, the characteristics of tropospheric ozone depletion events (ODEs) in the Arctic spring (April 2008) with satellite measured BrO and backtrajectories. Analysis of these data shows that the ODEs are due to either local halogen chemistry or short-range transport from adjacent high-BrO regions. Sometimes local ozone loss is surprisingly deep, particularly the unstable boundary layer at Churchill seems contribute to free-tropospheric BrO. Continually the influences of large-scale atmospheric patterns to the polar surface ozone are investigated. In years with frequent ODEs at Barrow and Alert, the WP teleconnection pattern is usually in its negative phase, during which the Pacific jet is strengthened but the storm track from western Pacific is weakened. Both factors tend to reduce the transport of ozone-rich airmass from mid-latitudes to the Arctic, creating a favorable environment for the Arctic ODEs. Comparison between Barrow and Alert shows the initiation of ODEs in spring is decided by the solar intensity and the termination is by the surface air temperature. Monthly frequency of ODEs also indicate the wind strength from the Arctic Ocean is largely influential to ODEs. The surface ozone at South Pole reveals year-round reversal trends during 3 decades, which is consistent with what lower-tropospheric temperature shows. Their strong correlation implies the possibility of large meridional mixing in warm conditions, which enhances the background level of ozone and nitrogen at South Pole.