Ozone variation in the tropical tropopause layer as seen from ozonesonde data

Abstract

Ozone variations with seasonal and intraseasonal timescales in the tropical tropopause layer (TTL) are investigated using a 5-year tropical ozonesonde data set from the SHADOZ (Southern Hemisphere Additional Ozonesondes) archive. The longitudinal ozone distribution in the tropical upper troposphere (TUT) shows a zonal wave one structure with maxima around the Atlantic and Africa and minima around the western Pacific throughout the year, while the annual variation shows maxima during northern summer to autumn at most longitudes. We compare the ozone distribution with the vertical temperature structure and found that the lapse rate is gradual (steep) at the ozone-enhanced (reduced) longitude and season. The east-west temperature structure and ozone variation in the TUT may be explained by the longitudinal variation of the large-scale atmospheric responses to the tropical heat source, which could govern both the temperature structure and the vertical transport processes. Ozone variability in the TUT is also large around the Atlantic and Africa and small around the western Pacific. However, the zonal wave one structure is not clear in the temperature variability and in the correlation coefficient between ozone and temperature, which can be related with wave activities around the tropopause. Remarkably large ozone variabilities with good correlation are observed in Africa during summer and in the central Pacific during autumn-winter. These are associated with large-scale equatorial waves, but the longitudinal variation of the wave activities does not seem to be an important factor in the zonal wave one structure of ozone.