On low value of surface ozone during winter in Delhi

Abstract

In this paper, our main aim has been to explain the low value of surface ozone during winter in Delhi (28^oN, 77^oE). First surface ozone data of Delhi from 1990-2012 has been examined. Analysis of data shows that the concentration of surface ozone is the lowest during winter (13.3ppbv in December-January) and the highest in summer (25.35ppbv in May-June). Also, during this period of study, surface ozone has an increasing trend ~ 0.3ppbv/year. Next an attempt has been made to explain the low value of surface ozone observed during winter. The concentration of NO and NO₂ determines the seasonal distribution of O₃. Low value of O₃ is explained when [NO₂]/[NO] ratio is ~1 and high value of surface ozone is explained when this ratio is ~2. The low value of [NO₂]/[NO] ratio and surface ozone during winter is due to the presence of fog.