Physical-Chemical Characteristics of the Atmosphere

Abstract

Abstract The hydrologic cycle, climate, weather patterns, and other large-scale functions are influenced by atmospheric processes. In addition, the transport and fate of contaminants in the atmosphere is strongly related to its various physical and dynamic properties. Atmospheric winds, for example, determine the pathways and speeds at which pollutants are transported away from sources such as cars and smoke stacks. Another physical process, the condensation of water vapor into rain and fog droplets, scavenges water-soluble pollutants from the atmosphere, ultimately determining the rate of their removal. In addition, the vertical variation of temperature greatly influences atmospheric stability and hence the turbulent mixing of polluted air with clean air. Temperature also affects reaction rates between chemical species, such as those involved in ozone formation in polluted urban environments. The chemical composition of the atmosphere is also critically important for both small- and global-scale pollution issues. The following sections provide a brief introduction to the physical and chemical properties of the atmosphere that are most relevant to our understanding of air pollution processes. The purpose here is to gain an overall understanding of air density, pressure, wind, water vapor, precipitation, radiation transfer, and temperature. We will not cover several important topics concerning the atmosphere, such as large-scale weather disturbances (e.g., hurricanes) or forecasting weather conditions for air pollution advisories. Interested readers should consult more comprehensive textbooks in atmospheric science for detailed information. Suggested references are listed at the end of this chapter.