Abstract
Abstract. This study examines the longitude-dependent decadal changes and trends of ozone for the boreal winter months during the period of 1960–2000. These changes are caused primarily by changes in the planetary wave structure in the upper troposphere and lower stratosphere. The decadal changes and trends over 4 decades of geopotential perturbations, defined as a deviation from the zonal mean, are estimated by linear regression with time. The decadal changes in longitude-dependent ozone were calculated with a simple transport model of ozone based on the known planetary wave structure changes and prescribed zonal mean ozone gradients. For December of the 1960s and 1980s a statistically significant Rossby wave track appeared over the North Atlantic and Europe with an anticyclonic disturbance over the Eastern North Atlantic and Western Europe, flanked by cyclonic disturbances. In the 1970s and 1990s statistically significant cyclonic disturbances appeared over the Eastern North Atlantic and Europe, surrounded by anticyclonic anomalies over Northern Africa, Central Asia and Greenland. Similar patterns have been found for January. The Rossby wave track over the North Atlantic and Europe is stronger in the 1980s than in the 1960s. For February, the variability of the regression patterns is higher. For January we found a strong alteration in the modelled decadal changes in total ozone over Central and Northern Europe, showing a decrease of about 15 DU in the 1960s and 1980s and an increase of about 10 DU in the 1970s and 1990s. Over Central Europe the positive geopotential height trend (increase of 2.3 m/yr) over 40 years is of the same order (about 100 m) as the increase in the 1980s alone. This is important to recognize because it implies a total ozone decrease over Europe of the order of 14 DU for the 1960–2000 period, for January, if we use the standard change regression relation that about a 10-m geopotential height increase at 300 hPa is related to about a 1.4-DU total ozone decrease.
Highlights
The assessment of the action of ozone chemistry, due to natural or anthropogeneous generated minor constituents at any location in the atmosphere, requires the knowledge of the dynamical-induced ozone variations
For January we found a strong alteration in the modelled decadal changes in total ozone over Central and Northern Europe, showing a decrease of about 15 DU in the 1960s and 1980s and an increase of about 10 DU in the 1970s and 1990s
Many observational and model studies of the ozone change have dealt with the zonal mean ozone variability only, but for a decade the need to study the structure of the longitude-dependent decadal ozone changes has become more and more the focus of investigations (e.g. Niu et al, 1992; Hood and Zaff, 1995; Peters and Entzian, 1996, 1999; Knudsen and Andersen, 2001; Hood and Soukharev, 2005)
Summary
The assessment of the action of ozone chemistry, due to natural or anthropogeneous generated minor constituents at any location in the atmosphere, requires the knowledge of the dynamical-induced ozone variations. This means that the longitude-dependent part was of the same order as the zonal mean part It was shown by Hood et al (1995) and by Peters et al (1996) that the decadal change in the large-scale wave structure in the geopotential height will cause the longitude-dependent decadal ozone change, due to different wave transport. With the help of a linear transport model for large-scale waves (Peters et al, 1996), we were able to calculate the decadal changes for all 4 decades This was possible because the NCEP reanalyses data set (Kalnay et al, 1996, upgrades) covers this period. Based on a regression analysis the annual zonally asymmetric relationship between total ozone and the 300 hPa geopotential was estimated by Entzian and Peters (2004). The column integral of it defines the decadal zonally asymmetric total ozone change
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
