T. J. Green

Seasonal Variation of the Photochemical Control of Ozone in the Lower Free Troposphere Based on Observations from the Free Tropospheric Experiments at Jungfraujoch in the Swiss Alps

Ozone is one of the most important trace gases in the troposphere being on the one hand an integral element in the control of the oxidizing capacity of the troposphere and on the other hand a climate gas. Although there is still a debate on the relative contribution from photochemistry and stratospheric intrusions to the origin of tropospheric ozone, the current consensus view is that photochemistry is the major contributor to the observed ozone levels [1, 2]. The ozone in the troposphere displays a clear seasonal cycle, which depends on a multitude of factors, such as the proximity to large source areas of ozone precursors, the geographical location and meteorological factors. In certain locations such as in the free troposphere or unpolluted sites in the Northern hemisphere tropospheric ozone shows a spring maximum but there has been much debate as to the origins of this phenomenon mainly due to the problems rising from the interpretation of measurements and the interactions of processes occurring on differing scales from the local to the global scale [3]. Several chemical theories were developed to explain the observed spring ozone maximum in the free troposphere of the Northern midlatitudes [4, 5].

Subproject TOR-2 Origins and Observations of the Spring Ozone Maximum. Theory and Experiment

Measurements of ozone throughout the troposphere clearly show an annual cycle. Over the last couple of decades it has become apparent that the measured annual cycle of ozone in certain locations shows a distinct maximum during spring and that the magnitude of the maximum seems to have increased. There has been much debate as to the origins of this phenomenon. There is broad agreement that much of the ozone found in the troposphere is of photochemical origin. In contrast, there is still no over-arching consensus as to the mechanisms that lead to the formation of the spring ozone maximum. Part of the problem would seem to lie in the interpretation of measurements and the interactions of processes occurring on differing scales from the local to the global scale.