Daily Ozone Patterns and AOT40 Index on the East Coast of the Iberian Peninsula

摘要

The results from the Valencian community air quality network show that within a natural pathway of air mass transport (e.g. a valley) three different O_3 diurnal patterns are clearly distinguished: high elevation (HE), mid-elevation (ME) and coastal sites (CE). HE are characterised by maintaining an almost constant high O_3 level throughout the day (no diurnal cycle). CE have maximum levels coinciding with daylight hours and close-to-zero O_3 levels at night (diurnal cycle). At ME the maximum values occur in the daylight hours; however, O_3 levels never drop to zero. These different patterns occur within a spatial range of 50 to 60 Km, which implies a huge spatial variability in the area, and may strongly affect the values of several indices, e.g. the AOT40. Thus, AOT40 indices for 3 months are calculated as a running value through the year and compared for the different O_3 patterns. Also, several daylight windows have been applied in the AOT40 calculations in order to check the sensitivity of the index to the daylight window choice and to the different daily ozone patterns, compared to the AOT40 calculated for hours with radiation>50W/m~2 (real daylight period) and to the total exposure dose (TED, 24h). It has been concluded that most windows estimate up to 90% of the TED in CE, and the estimations drop below 50% of the TED in non-diurnal cycle sites. This could be of importance for species whose period of stomatal conductance do not correspond to the daylight hours.