Thirty Years of Atmospheric CO2 Observations at the Plateau Rosa Station, Italy

The atmospheric background CO2 concentration is a key quantity for the analysis and evaluation of the ongoing climate change. Long-term CO2 observations have been carried out at the high Plateau Rosa mountain station, in the north-western Alps since 1989. The complete time series covers thirty years, and it is suitable for climatological analysis. The continuous CO2 measurements, collected since 1993, were selected, by means of a BaDS (Background Data Selection) filter, to obtain the hourly background data. The monthly background data series was analysed in order to individuate the parameters that characterise the seasonal cycle and the long-term trend. The growth rate was found to be 2.05 ± 0.03 ppm/year, which is in agreement with the global trend. The increased background CO2 concentration at the Plateau Rosa site is the consequence of global anthropic emissions, whereas the natural variability of the climatic system taken from the SOI (South Oscillation Index) and MEI (Multivariate ENSO Index) signals was detected in the inter-annual changes of the Plateau Rosa growth rate.

Background ozone in the southern Europe and Mediterranean area: influence of the transport processes

The troposphere is subject to continuous inputs, production and removal processes of ozone and its precursors from natural processes and human activities acting together within a very complex system. In order to assess the behaviour of background ozone in the Mediterranean area, a description of trends, seasonal and diurnal behaviours of free tropospheric ozone is provided. In the Mediterranean area and southern Europe the background tropospheric ozone concentration appears significantly affected by three main air mass transport processes: (i) transport of polluted air masses on regional and long-range scales, (ii) downward transport of stratospheric air masses, and (iii) transport of mineral dust from the Sahara desert. In this review of the literature of the last two decades, we present an overview of these phenomena, mainly monitored at high baseline mountain stations representative of background atmospheric conditions.

Continuous measurements of aerosol physical parameters at the Mt. Cimone GAW Station (2165 m asl, Italy)

Particle size distribution in the range 0.3<D(p)<or=20 microm, has been analysed from August 2002 to July 2006 at the GAW Station of Mt. Cimone (44.10 N, 10.42 E; 2165 m asl) in the northern Italian Apennines. The seasonal aerosol number size distribution, characterized by a bimodal shape, showed a behaviour typical for background conditions, characterized by highest values in summer and lowest in winter. The seasonal and diurnal variations of the larger accumulation mode (0.3<D(p)<or=1 microm average values: 26.15 cm(-3)) and the coarse mode (1<Dp<or=20 microm, average value: 0.17 cm(-3)) particle number concentrations (N 0.3-1 and N 1-20, respectively) exhibited a seasonal cycle with the highest values in spring-summer and the lowest value in autumn-winter. Except in winter, N 0.3-1 showed a clear diurnal variation with high values during day-time. N 1-20 showed a less marked diurnal variation (but with higher variability), suggesting the influence of non-continuous sources of coarse particle (i.e. Saharan dust events). Since July 2005, continuous measurement of black carbon (BC) concentrations was also available at the measurement site. On average low BC concentrations were recorded (average value: 0.28 microg m(-3)) even if a few events of high concentrations were recorded both in warm and cold season. Apart from wet scavenging processes which strongly affected aerosol concentrations, combined analysis of N 0.3-1, BC, meteorological parameters and air mass back-trajectories, suggests that the transport of polluted air masses from the lower troposphere (by local, regional or long-range transport) represents an important mechanism favouring N 0.3-1 and BC increases at Mt. Cimone. In particular, a trajectory statistical analysis for the period July 2005-July 2006 allowed the identification of the main source regions of BC and N 0.3-1 for Mt. Cimone: north Italy, west Europe and east Europe.