Highlights
► Dozen pollution episodes from Oct. to Feb in Hanoi associated with anticyclones after monsoon surges. ► 24-h concentrations of PM10, SO2, NO2, CO rise after surge and decline ahead of the next. ► Episodes caused by nighttime radiation and subsidence inversions in dry and humid monsoon phases. ► Distinct diurnal variations of pollutant concentrations observed in the two periods. ► Close pollution–meteorology association serve as a basis for warning and forecasting.