Diurnal Patterns in Global Fine Particulate Matter Concentration

Information about how fine particulate matter (PM2.5) concentrations vary over the course of a day on a global scale is limited. We used aggregated data sources to analyze the diurnal cycle of PM2.5 from more than 17 million hourly measurements at 3110 sites across the world, primarily in North America, Europe, and East Asia. The measurements reveal that diurnal PM2.5 cycles exhibit similar patterns across sites worldwide with a mean diurnal variability of 13.1%. PM2.5 cycles have a morning peak between 7:00 and 10:00 local solar time (LST) and an early nighttime peak between 21:00 and 23:00 LST, with an afternoon minimum occurring between 15:00 and 17:00 LST. Diurnal cycles are associated with dynamics of the atmospheric mixed layer as well as diurnal emission patterns, exhibiting an increased amplitude in regions with a large mixed layer height and mountainous terrain.