Solar eclipse induced changes in surface ozone at Ahmedabad

312-318Measurements of surface ozone and related gases were made at Ahmedabad was 79.2%. The diurnal increase in ozone concentration due to photo-oxidation of pollutants like CO, CH4 and non-methane hydrocarbons (NMHCs) observed on normal days after the sunrise was not observed until the time of maximum obscuration. In fact, there was a decrease in ozone concentration in the range of 18-21% at the maximum phase. Ozone levels were found to be lower even after the eclipse due to loss and delay in ozone production. The eclipse conditions were simulated in a photochemical box model which was used to calculate ozone changes. The model shows a decrease of ozone by about 16% as compared to a control day at the time of maximum obscuration. The model also shows significant role of boundary layer variations in the morning hours