On the role of ozone in long-term trends in the upper atmosphere-ionosphere system

J Laštovička

doi:10.5194/angeo-30-811-2012

Abstract

Abstract. Origin of long-term trends in the thermosphere-ionosphere system has been discussed since the beginning of trend studies. The two most prioritized explanations have been those via long-term increase of atmospheric concentration of greenhouse gases and long-term increase of geomagnetic activity throughout the 20th century. Secular changes of the Earth's main magnetic field play an important role in trends in a limited region. Recently, Walsh and Oliver (2011) suggested that the long-term cooling of the upper thermosphere (above 200 km) may be due largely to the stratospheric ozone depletion. Here, we show that the role of ozone is very important in the mesosphere and lower thermosphere but not in the upper thermosphere. The suggestion of Walsh and Oliver (2011) is based on historical (before 1988) data from Saint-Santin radar, whereas more recent data do not support their conclusion.

Highlights

The primary driver of long-term trends in the upper atmosphere and ionosphere is predominantly considered to be the increasing concentration of greenhouse gases, of CO2, e.g. Lastovicka et al (2006a)
The purpose of our short contribution is to show that Walsh and Oliver (2011) overestimate the role of ozone due to limited data set used, and that even if ozone may play some role, other trend drivers, including the increasing concentration of greenhouse gases dominate over ozone in driving trends at thermospheric altitudes of about 200– 500 km, studied by Walsh and Oliver (2011)
Summarizing, we may say that stratospheric ozone changes play a very important role in long-term trends in the MLT region, even though the dominant role is still played by greenhouse gases, except for stratopause and maybe lower mesosphere temperature in periods of dramatic changes of ozone concentration, when the ozone influence appears to be dominant

Summary

Introduction

The primary driver of long-term trends in the upper atmosphere (mesosphere and thermosphere) and ionosphere is predominantly considered to be the increasing concentration of greenhouse gases, of CO2, e.g. Lastovicka et al (2006a). There are other drivers of trends that play an important role, like long-term changes of geomagnetic activity, secular changes of the Earth’s magnetic field, probably long-term changes of activity of atmospheric waves coming from below, and in the mesosphere and lower thermosphere and related part of the ionosphere long-term changes of (stratospheric) ozone concentration (e.g. reviews by Lastovicka, 2009, or Qian et al, 2011). Walsh and Oliver (2011) came to conclusion that the long-term cooling of the thermosphere may be due largely to the stratospheric ozone depletion, and the greenhouse cooling may well not be detectable with current data sets. Ozone seems to play a very important but not dominant role in trends in the mesosphere and lower thermosphere (MLT region) (e.g. Lastovicka, 2009; Qian et al, 2011)

Evidence on the role of ozone in the MLT region

Ozone effect on the upper thermosphere and F-region ionosphere

Discussion and conclusions