A Mesoclimatological Classification System for Air Pollution Engineers

Abstract

A method of deriving 3 air pollution potential indexes based on selected climatic data and meso-climate topographic factors have been developed, though not yet adequately field tested, for use by engineers in choosing between alternate factory sites. Three indexes, one for general air pollution, one for photoreac-tive air pollutants, and one for fog-reactive air pollutants, the latter two based on the first one plus sunshine and humidity factors respectively, are presented. These indexes vary with locations, not with air pollutants or time. The first index, called the GSI (General Stagnation Index) is based on a series of national maps which present a variety of climatic parameters pertinent to air pollution potential for the mid-season months of July and October. These maps, useful by themselves, have been derived from climate records from 129 Weather Bureau airport stations and from radiosonde data. The parameters used include wind speed percentages in the 0-3 and 0-12 mile/hr categories, cloud cover percentages, a nighttime stagnation factor, and a vertical ventilation factor. The GSI provides a means of estimating the additional climatic stagnation that occurs in topographically sheltered areas due to width, height and area of the valley (if present), further modified by meso- and micro-climatological factors, such as angle and aspect of slope, solar intensity, sky cover and character of surface. Specialized wind speed summaries from a variety of topographical configurations in West Virginia resulted in a graph which may be helpful in such calculations for any sheltered location from a nearby measurement of relatively unrestricted air flow such as are typically measured at the Weather Bureau airport stations.Weaknesses and possible uses of the various stagnation indexes are discussed.