The Role of Convection in Tropical Ozone Trends (1998-2018) Based on
SHADOZ Profiles
Abstract
Quantifying variability in the lowermost stratosphere (LMS) is important
because of feedbacks among changing temperature, dynamics and species
like ozone. We used reprocessed Southern Hemisphere Additional
Ozonesondes data from 1998-2018 in a Multiple Linear Regression (MLR)
model to analyze variability and trends in free tropospheric (FT) and
LMS ozoneacross five well-distributed tropical regions. The MLR also
computed trends in a proxy for convection as determined from laminae in
each ozonesonde-radiosonde pair. Only the equatorial Americas exhibits
statistically significant annual trends in FT or LMS ozone. At the other
sites, ozonetrends occur in isolated layers during months when
convection has changed, February-April or July-November. Our results
imply that large FT ozone increases reported for populated tropical
areas may be caused by growing pollution overlying smaller changes
caused by perturbed dynamics. They also provide regional data for
evaluating LMS ozonetrends based on zonal averages of often sparse
satellite measurements