Accounting for local meteorological effects in the ozone time-series of Lovozero (Kola Peninsula)

The relationship between local meteorological conditions and the surface ozone variability was studied by means of statistical modeling, using ozone and meteorological parameters measured at Lovozero (250 m a.s.l., 68.5°N, 35.0°E, Kola Peninsula) for the period of 1999-2000. The regression model of daily mean ozone concentrations on such meteorological parameters as temperature, relative humidity and wind speed explains up to 70% of day-to-day ozone variability in terms of meteorological condition changes, if the seasonal cycle is also considered. A regression model was created for separated time scales of the variables. Short-term, synoptical and seasonal components are separated by means of Kolmogorov-Zurbenko filtering. The synoptical scale variations were chosen as the most informative from the point of their mutual relation with meteorological parameters. Almost 40% of surface ozone variations in time periods of 11-60 days can be explained by the regression model on separated scales that is 30% more efficient than ozone residuals usage. Quantitative and qualitative estimations of the relations between surface ozone and meteorological predictors let us preliminarily conclude that at the Lovozero site surface ozone variability is governed mainly by dynamical processes of various time scale rather than photochemistry, especially during the cold season

Accounting for local meteorological effects in the ozone time-series of Lovozero (Kola Peninsula)

International audienceThe relationship between local meteorological conditions and the surface ozone variability was studied by means of statistical modeling, using ozone and meteorological parameters measured at Lovozero (250 m a.s.l., 68.5°N, 35.0°E, Kola Peninsula) for the period of 1999-2000. The regression model of daily mean ozone concentrations on such meteorological parameters as temperature, relative humidity and wind speed explains up to 70% of day-to-day ozone variability in terms of meteorological condition changes, if the seasonal cycle is also considered. A regression model was created for separated time scales of the variables. Short-term, synoptical and seasonal components are separated by means of Kolmogorov-Zurbenko filtering. The synoptical scale variations were chosen as the most informative from the point of their mutual relation with meteorological parameters. Almost 40% of surface ozone variations in time periods of 11-60 days can be explained by the regression model on separated scales that is 30% more efficient than ozone residuals usage. Quantitative and qualitative estimations of the relations between surface ozone and meteorological predictors let us preliminarily conclude that at the Lovozero site surface ozone variability is governed mainly by dynamical processes of various time scale rather than photochemistry, especially during the cold season

Generation of layering in the upper arctic troposphere away from the jet stream

Ozone sounding databases for two stations, So-dankylä (67° N, 27° E) and Ny-Ålesund (79° N, 12° E) were used in order to investigate the generation of layering in the upper and middle troposphere of the Arctic. We concentrated on dry, ozone-rich and stable layers observed below the thermal tropopause under light wind conditions. This condition ensures that the observed layer is not a tropopause fold, a well-known phenomenon that develops within frontal zones near the jet stream. Selection criteria for ozone, humidity and stability anomalies of the tropopause fold detection algorithm were used here to pick out for detailed studies the most pronounced examples of laminae. For all these cases the meteorological situations were investigated in order to establish the origin of the observed layers. We found that layers could be classified into two groups. Laminae of the first group were observed equatorward of the jet stream and those of a second group were observed poleward of the jet. The meteorological situation for the first group resembles that for equatorward stratospheric streamer propagation. It was found that this group accounts for only a small fraction of the layers observed at Sodankylä and for none of those observed at Ny-Ålesund during the period investigated. A large case-to-case variability in the synoptic situation was observed for the second group of laminae, which were detected northward of the jet stream. Nevertheless, in about half of the cases, streamers of tropospheric air were found in the vicinity of the stations on the isentropic surfaces just above the detected stratospheric layers. Back trajectory analyses showed that these layers originated in the vicinity of the polar jet stream. We suppose that laminae-like structures in the troposphere were caused, in both groups, by equatorward (poleward) advection of the stratospheric (tropospheric) air, together with differential vertical shear. Forward-trajectory calculations suggest that, subsequently, a part of the stratospheric layers can mix irreversibly into the troposphere.Key words. Atmospheric composition and structure (pressure, density, and temperature; troposphere-composition and chemistry

Generation of layering in the upper Arctic troposphere away from the jet stream

Ozone sounding databases for two stations, Sodankylä (67° N, 27° E) and Ny-Ålesund (79° N, 12° E) wereused in order to investigate the generation of layering in the upper and middle troposphere ofthe Arctic. We concentrated on dry, ozone-rich and stable layers observed below the thermal tropopauseunder light wind conditions. This condition ensures that the observed layer is not a tropopause fold, awell-known phenomenon that develops within frontal zones near the jet stream. Selection criteria for ozone,humidity and stability anomalies of the tropopause fold detection algorithm were used here to pick out fordetailed studies the most pronounced examples of laminae. For all these cases the meteorological situationswere investigated in order to establish the origin of the observed layers. We found that layers could beclassified into two groups. Laminae of the first group were observed equatorward of the jet stream and thoseof a second group were observed poleward of the jet. The meteorological situation for the first groupresembles that for equatorward stratospheric streamer propagation. It was found that this group accounts foronly a small fraction of the layers observed at Sodankylä and for none of those observed at Ny-Ålesundduring the period investigated. A large case-to-case variability in the synoptic situation was observed for thesecond group of laminae, which were detected northward of the jet stream. Nevertheless, in about half ofthe cases, streamers of tropospheric air were found in the vicinity of the stations on the isentropic surfacesjust above the detected stratospheric layers. Back trajectory analyses showed that these layers originated inthe vicinity of the polar jet stream. We suppose that laminae-like structures in the troposphere were caused,in both groups, by equatorward (poleward) advection of the stratospheric (tropospheric) air, together withdifferential vertical shear. Forward-trajectory calculations suggest that, subsequently, a part of thestratospheric layers can mix irreversibly into the troposphere

Characterization of stratospheric water vapour vertical distribution in the Arctic from balloon observations during the recent winters

During the recent winters water vapour has been accurately measured from different Arctic sites using balloon-borne Lyman-alpha FLASH-B hygrosonde. Here we present the results of 18 balloon water vapour soundings conducted at Sodankylä (67 N) and Ny-Alesund (79 N) during 2003/04, 2004/05 and 2005/06 winters. The obtained data set allows case studies and detailed characterization of stratospheric water vapour vertical distribution within different conditions in the Arctic polar stratosphere.Water vapour vertical distribution in the Arctic lower stratosphere is primarily affected by the dynamical effects of polar vortex and by phase aggregation at the temperatures below ice PSC threshold. The measured H2O profiles carry the signatures of different processes occurring in the Arctic winter stratosphere and reveal a detailed view on the Arctic UT/LS water vapour distribution.The measurements clearly demonstrate typical differences in stratospheric water vapour concentration inside and outside the vortex; for example in the polar vortex of 2003/04 at 20 hPa the difference reaches 1.4 ppmv. Also it is pointed out that water vapour profiles obtained at the edge or close to the edge of vortex are characteristic by their laminated structure. As shown by the results of RDF-analysis this structure is not linked to dehydration but to differential advection of air masses originating from inside and outside the vortex. Thus water vapour is proved to be a valuable tracer for dynamical processes in the polar stratosphere. In the other case, the water vapour vertical profiles obtained at Ny-Alesund in January 2005 during the presence of PSCs clearly show the dehydration layers with reduced water vapour.Another focus is put here on the water vapour vertical distribution within the so called transition layer above the polar tropopause. The existence of this transition layer may be caused by diffusion of water vapour through the smeared polar winter tropopause, whereas the vertical structure of the H2O profile is affected by the dynamical processes.In addition the variability of water vapour at the hygropause and the distance between tropopause and hygropause are discussed

Ozone trends at northern mid- and high latitudes – a European perspective

The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC) which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes) playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds). Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent years are also considered, namely the tendency for cold winters to become colder