Surface ozone measurements at Anantapur (AP), India

The ozone-mixing ratio in ambient air is being measured for every 15 min at Anantapur, a semi-arid zone since April 2001 and analysed. The results show diurnal, day-to-day and seasonal variability. A typical diurnal variation shows an increase during the day, reaching maximum around local noon. However, the diurnal minimum is reached about an hour after sunrise but not during night. The other important feature observed is that the magnitude of the diurnal variation as well as the absolute concentrations of ozone are much higher in winter and summer than in autumn. While the average ozone during noon hours in autumn months is about 25 ppbv, it becomes as high as 50 ppbv during winter and summer months.