Variability in the vertical distribution of ozone over a subtropical site in India during a winter month

Six sets of electrochemical ozonesondes along with radiosondes were launched during 11–29 December 2004 from Kanpur (26.03N, 80.04E). Large variabilities in the vertical distribution of ozone have been observed during the campaign period. Higher ozone levels as compared to the average of all the profiles during this period have been observed in the height ranges of 3–7 and 10–18 km on December 18 and 25, respectively. Ozone levels in the 11–14 km range were observed to be much lower on December 29. These events have been analyzed in detail using meteorological parameters, back trajectories and potential vorticity. Higher ozone on December 18 may be associated with lateral transport from Africa and Gulf countries, where higher CO had been observed along the trajectory path. However, on December 25, enhanced ozone layers could be associated with transport from the stratosphere. Potential vorticity data suggest that a jet stream from midlatitude was approaching this location along the isentropic surface (350 K) towards the southeast direction. The lower ozone observed on December 29 originated from the marine region near the equator. These sharp changes in this period reflecting changing meteorology have given evidence of transport of ozone from different regions including stratospheric intrusion.