Earlier Seasonal Maximum in Lower Tropospheric Ozone at Northern Mid-Latitudes
Abstract
At northern mid-latitudes the abundance of tropospheric ozone has changed, increasing by a factor of approximately 2 since the 1950s. The cause of this increase is generally attributed to increasing anthropogenic precursor emissions, but present chemical and transport models cannot quantitatively reproduce its magnitude. Here we show another manifestation of changes in ozone abundance, a shift of the seasonal cycle at northern mid-latitudes so that the observed peak concentrations now appear earlier in the year than they did in previous decades. The magnitude of this shift has been about 3 to 6 days per decade since the 1970s. We will discuss several possible reasons for these changes, including a greater contribution of stratospheric ozone transport to the troposphere with changing climate and a shift of emissions of ozone precursors to more southerly latitudes. There is a need for detailed modeling to fully establish the causes; investigating these hypotheses will provide useful guidance for improving global chemistry-climate models as well as stringent tests of the model results.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A43E0200P
- Keywords:
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- 0322 ATMOSPHERIC COMPOSITION AND STRUCTURE / Constituent sources and sinks;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry