The latitudinal ozone variability study using wavelet analysis

Abstract

The ozone variability on time scales of the solar rotation was studied using zonal averaged total ozone content (TOC) TOMS data, covering a time span from 1978 to 2005. The ozone variability was found to increase strongly with latitude outside of the tropics (35°S–35°N). The reasons for the higher ozone variability are dynamical processes. The asymmetric distribution of the ozone variability over both hemispheres at latitudes higher than 35° is also dynamically generated. To study the solar rotational activity effects on total ozone, wavelet analysis is used. For a sequence of different latitudes, Morlet wavelet spectra of ozone variability were constructed for periods up to 55 days. The wavelets were scale averaged over a period interval from 20 up to 36 days, which is a typical time scale for solar activity variations, generated by solar rotation and by unevenly distributed active regions over the solar disk. With the help of the averaged wavelet spectra, a Hovmöller (latitude–time) diagram for the TOC was constructed. A seasonal variation of the border between lower and higher ozone variations was observed. The highest ozone variations in the tropical regions are extended meridionally from about 20°S up to 20°N and were observed during a time interval of several months when the equatorial ozone variation was nearly in phase with the solar activity variation. This suggests that the low ozone variations in the tropics are solar induced.