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The attention paid to changes in atmospheric concentrations of greenhouse gases has recently increased, with particular regard to the relationships between variations of their annual trends and of their shorter-period fluctuations on the one hand, and some geophysical and biological natural processes (like atmospheric transport, volcanic eruptions, ENSO events, seasonal vegetation cycles, and so on) on the other hand. Careful analysis and interpretation of the above relationships, in fact, can often disclose unknown mechanisms acting on modulations of these gases and make it possible for us to better understand the contributions made to them by natural causes, contrasted with anthropogenic ones. This paper presents and discusses the results of a series of CO2 air concentration data, measured at Plateau Rosa (3480 m a.s.l.—Italian Western Alps) over a period of about four years, and correlated with atmospheric transport processes on synoptic scale. These results have shown the leading role played by some kinds of atmospheric circulation patterns in creating situations of not fully mixed air streams (and, as such, not representative of background conditions) and have also suggested a «meteorological» selection scheme for CO2 data to be used in evaluating more reliable annual trends.

Heat island contribution to the 148 year temperature series of Milan is evaluated by comparing Milan urban series with Milan airport series and with other European and North Hemispheric series. The heat island trend is then compared with the growth of the city radius and finally two relations between the city radius and the efffects of the heat island are determined.

The aim of this paper is to study the phenomenon of acid smut fall-out. An analitycal model describing the estimate of their down-wind fall-out distance as a function of their mean size is presented. Some considerations concerning the different smut morphology are carried out in order to assess the fall-out rate to be introduced into the model. Changes in the fall-out distance are related to the various heights reached by particles in the plume, and to the vertical wind profile. To provide a first validation, some comparisons between the model predictions and the observed smuts, collected during a compaign near a power plant, are carried out.

The characteristics of the air quality monitoring station of Brera Tower are described. The station is focused on the study of air pollution in the urban area and on the aerosol chemistry and reactivity in the atmosphere. The influence of meteorological parameters is also taken into account. Results about the concentration, the chemical composition and the size distribution of suspended particulate matter and about the ionic composition and acidity of rain are also presented.

This paper presents a climatological diffusion model for computing seasonal sulphur dioxide concentrations. The area under investigation is located in the Po Valley (Northern Italy), and is characterized by prevailing conditions of weak winds, with the presence of mountain and valley breeze. A large number of sulphur dioxide sources are located in this area: they are both urban emissions (due to home heating) and industrial emissions. A physical parametrization of the planetary boundary layer was achieved by using the results of experimental campaigns in the site. A detailed source inventory was compiled in order to supply correct input to the model. The paper presents the results obtained by simulations over a period of 2 years. The agreement between measured and computed concentrations confirms the soundness of the physical parametrizations of the model and makes it suitable to use it for planning future urban and industrial emissions in the area.

Several experimental studies, carried out in recent years in the Po Valley, regarding typical meteorological conditions and the applications of the most recent dispersion models, enabled us to state the optimal chimney height related to air pollution problems. It appears that a chimney (170÷180) meters high is sufficient to ensure sufficient dispersion of plumes emitted into the atmosphere to ensure low levels of SO2 concentration at the ground, even during the most critical weather conditions.

Comparison of turbulent-diffusion parametersσ v andσ z, evaluated through different experimental tests carried out in the Po Valley in the range (102÷104) m downwind the source, under neutral and unstable conditions, is presented and discussed. Two kinds of methods of tracer dispersion were adopted. The first one dealth with no-lift balloon diffusion in the range (102÷103) m, while the second one was relative to SF6 dispersion in the range (103÷104) m. In the present paper the two sets of data are joined and a single series of best-fit curves covering the whole measured range (102÷104) m is derived. The results show different behaviours forσ y andσ z; in fact, it is possible to extrapolateσ y trends from one set of data (SF6) to the other one (no-lift balloons) without changing the analytical expression and the values of their coefficients. Forσ z, instead, some new considerations are needed. In fact, for the unstable categories here considered (B/C andC) it is necessary to change the analytical form of theσ z trend. This is due to the effect of convection resulting in an increase of dσ z/dx. Finally, the exponent of the sampling time τ, in theσ y vs. τ relationship, was found equal to 0.2, in the range (16÷128) min.

It is aim of this work to acquire information useful to understand the trasborder transport of atmospheric trace elements passing through the Alps. To this end it is necessary to know with a good accuracy the atmospheric movements and their thermodynamic structure at the synoptic scale. With these objects in view, from the one hand a measuring campaign on the Western Alps (Sestrieres Pass) has been performed, during which the concentration of some gaseous constituents of the atmosphere (O3, NO x , SO2) and thermodynamic structure of the air masses which carried them have been measured; on the other hand, synoptic air trajectoris (based on the Reading ECMWF data) passing through that measuring station have been computed. Such calculations have been carried out by two algorithms: the first one computes the 3D air mass trajectory on the ground of the three wind velocity components only (which are known on the Reading model grid points). The second one behaves as the first one as far as the horizontal movement is concerned, but compels the atmosphere to move along surfaces of equal pseudopotential temperature (isentropic surface) in the vertical plane.

The problem of the internal boundary layer (IBL) development at two Italian coastal sites (La Spezia and Montalto di Castro) has been investigated. Among the numerous IBl empirical models found in the literature, which are briefly introduced and discussed, we choose the Nanticoke model because it seems to deal with the physical problem in a more complete and satisfactory way. In fact it explicitly considers two different time scales (the advective and the diurnal one) contemporary acting on the phenomenon. The results of the comparison between the measured data and the ones calculated by means of the Nanticoke model were encouraging even if the influence of the complex topography and orography was felt.

Particulate-matter release into the stack effluents of a large coal-fired power station was characterized. Particulate samplings were carried out in the chimney, downstream the electrostatic precipitation system, by means of an isokinetic probe. Concentration and size distribution of total particulate mattern as well elemental composition as a function of particle size were detemined. Concentrations of up to 24 elements were measured for whole filters by PIXE and AAS technique. Element enrichments in smaller particles and in emitted ashes and their behaviours in combustion are also studied.

In September 1979, the Turbigo power plant of ENEL hosted the fourth European experiment on the remote sensing of atmospheric dispersion and boundary layer structure sponsored by the Commission of the European Communities (CEC). The exercise was particularly aimed at studying nonstationary diffusion processes, under low wind and convectively unstable conditions; other situations, typical of up- and down-valley breeze regimes, were observed as well. The campaign produced a large amount of information, the analysis of which is still under development. This paper highlights the overall results obtained by the joint effect of many teams, simultaneously operating both conventional and advanced remote-sensing instruments. In particular, it describes and discusses the results connected to a few specific objectives, representing the main characteristics of the conditions peculiar to this experiment and to the site climatology.

The analysis of daily precipitation data at many weather stations in Alpes and Po Valley gives evidence of a “tidal” influence from luni-solar gravitational fields. Periodicities in the 13–15 and 27–30 day time interval have been frequently extracted from data series (ENEL data: 1970–1981 years; SMR data: 1961–1980 years), by using distinct methods. The tidal influence does not appear to be strictly constant with time, as the possible result of a modulation effect of luni-solar cycles having similar periods. Time variations of daily precipitation data as a function of some particular cycles show that gravitational tides affect heavy rainfalls more than mean precipitation values. The different contribution of “semi-monthly” oscillations with season underlines a more distinguishable regime of vertical motions in Winter with respect to Summer. In investigating joint effects of different luni-solar components, the inverse Fourier transform method points out superimposed influences in correspondence to some years (1966 and 1976), climatologically very interesting, and this might assist in the previsional studies of extreme precipitation.

The radioactive cloud released during the Chernobyl accident reached the Po Plain and Lombardy in the night of April 30, 1986; the cloud remained in the northern Italian skies for a few days and then disappeared either dispersed by winds or washed by rains. The evidence in the atmosphere of radionuclides as tellurium, iodine, cesium was promply observed by the Istituto di Fisica. The intense rain, in the first week of May, washed the radioactivity and the fallout contaminated the land, soil, grass and vegetables. The present work concerns the overall contamination of the Northern Italy territory and in particular the radioactive fallout in the Alpine region. Samples of soil have been measured at the gamma-spectroscope; a linear correlation is found between the radionuclide concentration in soil samples and the rain intensity, when appropriate deposition models are considered. A number of measurements has been done on Lake Como ecosystem: sediments, plankton, fishes and the overall fallout in the lake area have been investigated.