Trends and variability of midlatitude stratospheric water vapour deduced from the re-evaluated Boulder balloon series and HALOE

This paper presents an updated trend analysis of water vapour in the lower midlatitude stratosphere from the Boulder balloon-borne NOAA frostpoint hygrometer measurements and from the Halogen Occulation Experiment (HALOE). Two corrections for instrumental bias are applied to homogenise the frostpoint data series, and a quality assessment of all soundings after 1991 is presented. Linear trend estimates based on the corrected data for the period 1980–2000 are up to 40% lower than previously reported. Vertically resolved trends and variability are calculated with a multi regression analysis including the quasi-biennal oscillation and equivalent latitude as explanatory variables. In the range of 380 to 640 K potential temperature (≈14 to 25 km), the frostpoint data from 1981 to 2006 show positive linear trends between 0.3±0.3 and 0.7±0.1%/yr. The same dataset shows trends between −0.2±0.3 and 1.0±0.3%/yr for the period 1992 to 2005. HALOE data over the same time period suggest negative trends ranging from −1.1±0.2 to −0.1±0.1%/yr. In the lower stratosphere, a rapid drop of water vapour is observed in 2000/2001 with little change since. At higher altitudes, the transition is more gradual, with slowly decreasing concentrations between 2001 and 2007. This pattern is consistent with a change induced by a drop of water concentrations at entry into the stratosphere. Previously noted differences in trends and variability between frostpoint and HALOE remain for the homogenised data. Due to uncertainties in reanalysis temperatures and stratospheric transport combined with uncertainties in observations, no quantitative inference about changes of water entering the stratosphere in the tropics could be made with the mid latitude measurements analysed here

Trajectory matching of ozonesondes and MOZAIC measurements in the UTLS – Part 2: Application to the global ozonesonde network

Both balloon-borne electrochemical ozonesondes and MOZAIC (measurements of ozone, water vapour, carbon monoxide and nitrogen oxides by in-service Airbus aircraft) provide very valuable data sets for ozone studies in the upper troposphere/lower stratosphere (UTLS). Although MOZAIC's highly accurate UV-photometers are regularly inspected and recalibrated annually, recent analyses cast some doubt on the long-term stability of their ozone analysers. To investigate this further, we perform a 16 yr comparison (1994–2009) of UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC. The analysis uses fully three-dimensional trajectories computed from ERA-Interim (European Centre for Medium-Range Weather Forecasts Re-analysis) wind fields to find matches between the two measurement platforms. Although different sensor types (Brewer-Mast and Electrochemical Concentration Cell ozonesondes) were used, most of the 28 launch sites considered show considerable differences of up to 25% compared to MOZAIC in the mid-1990s, followed by a systematic tendency to smaller differences of around 5–10% in subsequent years. The reason for the difference before 1998 remains unclear, but observations from both sondes and MOZAIC require further examination to be reliable enough for use in robust long-term trend analyses starting before 1998. According to our analysis, ozonesonde measurements at tropopause altitudes appear to be rather insensitive to changing the type of the Electrochemical Concentration Cell ozonesonde, provided the cathode sensing solution strength remains unchanged. Scoresbysund (Greenland) showed systematically 5% higher readings after changing from Science Pump Corporation sondes to ENSCI Corporation sondes, while a 1.0% KI cathode electrolyte was retained

Variability and trends in total and vertically resolved stratospheric ozone

International audienceTrends in ozone columns and vertical distributions were calculated for the period 1979?2004 based on the three-dimensional ozone data set CATO (Candidoz Assimilated Three-dimensional Ozone) using a multiple linear regression model. CATO has been reconstructed from TOMS, GOME and SBUV total column ozone observations in an equivalent latitude and potential temperature framework and offers a pole to pole coverage of the stratosphere on 15 potential temperature levels. The regression model includes explanatory variables describing the influence of the quasi-biennial oscillation, volcanic eruptions, the solar cycle, the Brewer-Dobson circulation, Arctic ozone depletion, and the increase in stratospheric chlorine. The effects of displacements of the polar vortex and jet streams due to planetary waves, which may significantly affect trends at a given geographical latitude, are eliminated in the equivalent latitude framework. Ozone variability is largely explained by the QBO and stratospheric aerosol loading and the spatial structure of their influence is in good agreement with previous studies. The solar cycle signal peaks at about 30 to 35 km altitude which is lower than reported previously, and no negative signal is found in the tropical lower stratosphere. The Brewer-Dobson circulation shows a dominant contribution to interannual variability at both high and low latitudes and accounts for some of the ozone increase seen in the northern hemisphere since the mid-1990s. Arctic ozone depletion significantly affects the high northern latitudes between January and March and extends its influence to the mid-latitudes during later months. The vertical distribution of the ozone trend shows distinct negative trends at about 18 km in the lower stratosphere with largest declines over the poles, and above 35 km in the upper stratosphere. A narrow band of large negative trends extends into the tropical lower stratosphere. Assuming that the observed negative trend before 1995 continued to 2004 cannot explain the ozone changes since 1996. A model accounting for recent changes in EESC, aerosols and Eliassen-Palm flux, on the other hand, closely tracks ozone changes since 1995

Volatile Organic Compounds in the Po Basin. Part A: Anthropogenic VOCs

Measurements of volatile organic compounds (VOCs) were performed in the Po Basin, northern Italy in early summer 1998 within the PIPAPO project as well as in summer 2002 and autumn 2003 within the FORMAT project. During the three campaigns, trace gases and meteorological parameters were measured at a semi-rural station, around 35 km north of the city center of Milan. Low toluene and benzene concentrations and lower toluene to benzene ratios on weekends, on Sundays, and in August enabled the identification of a ‘weekend' and a ‘vacation' effect when anthropogenic emissions were lower due to less traffic and reduced industrial activities, respectively. Recurrent nighttime cyclohexane peaks suggested a periodical short-term release of cyclohexane close to the semi-rural sampling site. A multivariate receptor model analysis resulted in the distinction of different characteristic concentration profiles attributed to natural gas, biogenic impact, vehicle exhaust, industrial activities, and a single cyclohexane sourc

The effects of resistance training on well-being and memory in elderly volunteers

Objective: to determine the short- and long-term effects of resistance training on muscle strength, psychological well-being, control-beliefs, cognitive speed and memory in normally active elderly people. Methods: 46 elderly people (mean age 73.2 years; 18 women and 28 men), were randomly assigned to training and control groups (n = 23 each). Pre- and post-tests were administered 1 week before and 1 week after the 8-week training intervention. The training sessions, performed once a week, consisted of a 10 min warm-up phase and eight resistance exercises on machines. Results: there was a significant increase in maximum dynamic strength in the training group. This training effect was associated with a significant decrease in self-attentiveness, which is known to enhance psychological well-being. No significant changes could be observed in control-beliefs. Modest effects on cognitive functioning occurred with the training procedure: although there were no changes in cognitive speed, significant pre/post-changes could be shown in free recall and recognition in the experimental group. A post-test comparison between the experimental group and control group showed a weak effect for recognition but no significant differences in free recall. Significant long-term effects were found in the training group for muscular strength and memory performance (free recall) 1 year later. Conclusion: an 8-week programme of resistance training lessens anxiety and self-attentiveness and improves muscle strengt

Symbiosis-stimulated chitinase isoenzymes of soybean (Glycine max (L.) Merr.)

Isoforms of endochitinase in soybean were studied in relation to root symbiosis. Five selected cultivars differing in their nodulation potential were inoculated with two strains of Bradyrhizobium japonicum, the broad host-range Rhizobium sp. NGR234, and with the mycorrhizal fungus Glomus mosseae. Total chitinase activity in nodules was up to 7-fold higher than in uninoculated roots and in mycorrhizal roots. The chitinase activity in nodules varied depending on the strain-cultivar combination. On semi-native polyacrylamide gels, four acidic isoforms were identified. Two isoforms (CH 2 and CH 4) were constitutively present in all analysed tissues. The other two isoforms (CH 1 and CH 3) were strongly induced in nodules and were stimulated in mycorrhizal roots as compared to uninoculated roots. The induction of CH 1 varied in nodules depending on the soybean cultivar. This isoform was also stimulated in uninfected roots when they were treated with tri-iodobenzoic acid, rhizobial lipochitooligosaccharides (Nod factors) and chitotetraose. CH 3 was not affected by these stimuli indicating that this isoform could represent a marker for enzymes induced in later stages of the symbiotic interaction

Volatile Organic Compounds in the Po Basin. Part B: Biogenic VOCs

Measurements of volatile organic compounds (VOCs) were performed in the Po Basin, northern Italy in early summer 1998, summer 2002, and autumn 2003. During the three campaigns, trace gases and meteorological parameters were measured at a semi-rural station, around 35 km north of the city center of Milan. Bimodal diurnal cycles of isoprene with highest concentrations in the morning and evening were found and could be explained by the interaction of emissions, chemical reactions, and vertical mixing. The diurnal cycle could be qualitatively reproduced by a three-dimensional Eulerian model. The nighttime decay of isoprene could be attributed mostly to reactions with NO3, while the decay of the isoprene oxidation products could not be explained with the considered chemical reactions. Methanol reached very high mixing ratios, up to 150 ppb. High concentrations with considerable variability occurred during nights with high relative humidities and low wind speeds. The origin of these nighttime methanol concentrations is most likely local and biogenic but the specific source could not be identifie

Quantification of the impact in mid-latitudes of chemical ozone depletion in the 1999/2000 Arctic polar vortex prior to the vortex breakup

International audienceFor the winter 1999/2000 transport of air masses out of the vortex to mid-latitudes and ozone destruction inside and outside the northern polar vortex is studied to quantify the impact of earlier winter (before March) polar ozone destruction on mid-latitude ozone. Nearly 112 000 trajectories are started on 1 December 1999 on 6 different potential temperature levels between 500?600 K and for a subset of these trajectories photo-chemical box-model calculations are performed. We linked a decline of ?0.9% of mid-latitude ozone in this layer occurring in January and February 2000 to ozone destruction inside the vortex and successive transport of these air masses to mid-latitudes. Further, the impact of denitrification, PSC-occurrence and anthropogenic chlorine loading on future stratospheric ozone is determined by applying various scenarios. Lower stratospheric temperatures and denitrification were found to play the most important role in the future evolution of polar ozone depletion