Characteristics of sea-land breeze and its relationship with pollutant concentrations during winter and spring in 2017 in Zhangzhou

Based on meteorological observational data in Zhangzhou, Fujian province and the south island in 2017, sea-land breeze days were distinguished using statistical analysis and manual correction methods.In combination of synoptic situation and observed pollutant concentrations, the characteristics of sea-land breeze days and its relationship with pollutant concentrations were analyzed.The results show that the number of days with sea-land breeze in Zhangzhou is 2.2 times as large as that observed at an island station.Sea-land breeze occurs more frequently in spring and summer and less in autumn and winter.In winter, synoptic situations on the sea-land breeze days are dominated by transformed surface cold high, high-pressure rear, and warm sector ahead of front, and are accompanied by small pressure gradient, high air temperature, small wind speed, long sunshine duration, low humidity, and small cloud cover, which is unfavorable for the dilution and diffusion of pollutants.During sea-land breeze days, concentrations of all pollutants (except for O₃) are 2-3 times as large as that on the systematic wind days, and particulate matter concentrations are especially high.Unlike in winter, sea-land breeze in spring contributes to high particulate matter and even higher O₃, although the dominated synoptic situation and meteorological conditions in both seasons are similar to each other.All pollutant concentrations on sea-land breeze days are 1-2 times higher than that on systematic wind days, and O₃ concentration is easy to exceed the standard level on sea-land breeze days.Although the annual occurrence frequency of land-sea breeze is less than 30% in Zhangzhou, its unique diurnal variation and local circulation structure have an important impact on pollutant accumulation and transport.