Ozone within and below the west coast temperature inversion

Abstract

The oxidant concentration in the air over the San Francisco Bay Area and the Pacific Ocean was measured up to an altitude of 2500 m and the observed distribution in the vertical and horizontal has been related to the characteristics and behavior of the west coast temperature inversion. Vertical time sections at fixed points and vertical cross sections were constructed of oxidant concentration, temperature, humidity and winds measured from aircraft and radar. The oxidant concentration in polluted air is strongly dependent on the destruction rate. The mean destruction rate within the surface layer depends directly on the intensity of eddy mixing and inversely on the square of the depth of the vertical mixing. Thus, the existence of a temperature inversion does not necessarily lead to a high concentration of oxidants, since the destruction rate may be high in a shallow mixing layer. The highest oxidant concentration was observed almost invariably at the edges of the west coast marine inversion, where pollutants are available for ozone production and the mixing layer is deep. Explanations are offered for the maxima of ozone that often occur above the inversion base. Distribution patterns of oxidants clearly depict the waving of the inversion layer.