Emissions from anthropogenic and natural sources into the atmosphere are determined in large measure by prevailing weather conditions through complex physical, dynamic, and chemical processes. Air pollution episodes are characterized by degradation in air quality as reflected by the increase in ambient concentrations of specific pollutants, such as ozone and particulate matter. Air quality degradation is associated with adverse health effects; examples are the aggravation of respiratory and cardiovascular disease. During the ozone season (May to September), ozone reaches its peak concentrations, and consequently exerts its most severe potential health impacts, under high pressure conditions at the surface that are associated with clear skies and high temperatures. Formation of secondary particulate matter—for example, sulfate and organic aerosols (both present mainly in the fine size fraction)—also increases in the same weather conditions during summer in the eastern United States.

To identify regional weather characteristics in terms of their relationship to air pollution and consequent health impacts, we use a weather classification analysis method that presents results in terms of eight air-mass patterns. The synoptic weather type classification scheme developed by Sheridan (2002) is used to analyze weather and air quality data for the Charlotte metropolitan statistical area in North Carolina (population: over 1 million). We compare the Sheridan scheme to one based on cluster analysis that includes parameters such as temperature, pressure, and wind speed and direction. A number of types of hierarchical and nonhierarchical cluster analysis methods are examined, and discriminant analysis is also applied to develop a predictive method. We discuss the various air-mass types in terms of their origin (e.g., tropical versus polar) and moisture content. We examine data for ozone, particulate matter (PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide from January 1996 through December 2004 at several monitoring sites within the greater Charlotte urban area. Data for all these pollutants show considerable variability, which is dependent on the weather pattern. Relationships between air pollutant concentrations and weather patterns are characterized and presented using synoptic classification approaches.

Reference:

Sheridan, S.C., The redevelopment of a weather-type classification scheme for North America, Int. J. Climatol., 22, 51-68, 2002.