Time and space variability in air quality

Abstract

Air quality varies in both time and space. This is to be expected, but the complication for network design is that the variations are neither random nor well behaved. There are, in fact, several inter-related factors which affect the time and space fields of the concentrations of trace substances. Some of these factors are: (1) non-uniform emission rates (irregular distribution of sources and of source heights; daily, weekly and annual cycles of emissions; long-term changes in source locations and strengths); (2) large-scale meteorological factors (daily and annual weather cycles; synoptic weather patterns; long-term climatic oscillations and trends); (3) modulations in the large-scale meteorological factors owing to local topography and urban effects; (4) variations in the rates of chemical transformations and deposition (diurnal cycles, precipitation scavenging, uptake by vegetation, etc.); (5) random fluctuations (owing to atmospheric turbulence, etc.).