Intraseasonal variation of visibility in Hong Kong

Visibility is one of the parameters for indicating air pollution. In this study, visibility variation in Hong Kong during summer and winter is investigated. Visibility in Hong Kong has clear intraseasonal variation. Examination of different environmental parameters suggests that the intraseasonal component dominates the overall circulation anomalies in both summer and winter. Associated with the intraseasonal variation of environmental parameters, obvious variation in visibility impairment is found in both summer and winter. In summer, local visibility and air quality are found to be significantly affected by the (MJO) and the 10-30-day intraseasonal oscillation (ISO) through modulation of associated atmospheric circulations. In winter, the modulation effects appear to be weaker due to the southward shift of the associated convection. The results in this study highlight the importance of the ISO in contributing to the overall variation in visibility in Hong Kong, and provide useful implications for the development of possible mitigation strategies associated with visibility impairment and air pollution in Hong Kong.