Spatio-temporal co-variability of air pollutants and meteorological variables over Haqel and Jeddah, Saudi Arabia

This study presents a first simultaneous trend and magnitude assessment of the air pollutants (CO, H2S, SO2, NO2, NO, NOx, O3 and PM10), and meteorological variables (rainfall or RF, relative humidity or RH, atmospheric pressure or PR, temperature or TC, wind speed or WS and wind direction or WD) in the city of Haqel and at four different locations in the city of Jeddah, in Saudi Arabia, for a continuous 5-year period (2008−2012). The spatio-temporal co-variations of air pollutants in terms of their diurnal, weekly, seasonal and annual cycles, and their relationship with meteorological conditions, along with the estimates of the weekend effect, are described. A decreasing annual trend was observed for most air pollutants analyzed except for O3 and PM10. The CO, NO2, NO and NOx displayed a strong weekend effect. A percentile-based change analysis displayed an increase in concentrations for O3 (PM10) in the lower (higher) percentiles from the first to second half of the study period. The study identified 12 cyclonic weather events during the 5-year time period associated with high PM10 concentrations (> 500 µg m-3) relative to a mean value of 102 µg m-3, with a standard deviation value of 179 µg m-3. The study also analyzed the impacts of several mid-latitude anti-cyclonic events on air pollutant concentrations and found a significant change in air pollutant concentrations (CO, SO2, NO2, NO, NOx, O3 and PM10) and meteorological variables (RH, PR, TC, WS, and WD) associated with stagnant upper air conditions during the atmospheric blocking.