How the High Ozone Concentrations in Summer Depend on Air Temperature

Abstract

Correlations between high concentrations of ozone in ambient air and high air temperatures such as daily maxima in a target area are studied with using official monitoring data. The summer ozone data from the Tokyo metropolitan area in two periods since 2001, during which the ozone precursor (NO_x and NMHC) concentration levels were kept comparatively stable, were statistically analyzed along with temperature data from the Saitama AMeDAS (Urawa). The maximum ozone concentration, when averaged for every summer, is highly correlated the with number of days with a clear sky, rather than the air temperature. In order to focus on the contribution of the air temperature, exclusion of cloudy/rainy days from the statistics, and furthermore, extraction of sample days of similar weather and wind patterns, become required. As a result, the daily maxima of the ozone concentrations have a clear dependence on the maximum temperature only in its range above 33 deg. C, and is sharply influenced at about 37 deg. C and above, which occurs frequently in recent years. In this very high temperature range, no ozone reduction due to decreases in NMHC is observed in the examined periods.