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Papers by Riccardo Santaguida
Atmospheric Research, 2010
The time-patterns of ground-level solar irradiance during the solar eclipse of 29 March, 2006, we... more The time-patterns of ground-level solar irradiance during the solar eclipse of 29 March, 2006, were observed at three Italian stations (Lampedusa, Mt. Cimone and Bologna) using different radiometric techniques. The global irradiance measured at the sites was found to reach the minimum at times not coinciding with those predicted by radiative transfer model evaluations, with ahead or lag times depending on the optical characteristics of the surface-atmosphere system in the areas surrounding of the stations. This different behaviour has been mainly attributed to the different influence of the environmental conditions on the diffuse radiance component measured at the observation sites. The present results indicate that the incoming diffuse radiance recorded at the three stations was appreciably affected by contributions arising from extended regions of about 30-100 km range from the stations. Such an explanation agrees very well with the theoretical evaluations obtained in earlier studies. The surrounding environmental areas of impact at ultraviolet wavelengths have been found to be wider than those in the visible and near-infrared spectral ranges.
Applied Optics, 2006
The ultraviolet narrowband filter radiometer (UV-RAD) designed by the authors to take ground-base... more The ultraviolet narrowband filter radiometer (UV-RAD) designed by the authors to take ground-based measurements of UV solar irradiance, total ozone, and biological dose rate is described, together with the main characteristics of the seven blocked filters mounted on it, all of which have full widths at half maxima that range 0.67 to 0.98 nm. We have analyzed the causes of cosine response and calibration errors carefully to define the corresponding correction terms, paying particular attention to those that are due to the spectral displacements of the filter transmittance peaks from the integer wavelength values. The influence of the ozone profile on the retrieved ozone at large solar zenith angles has also been examined by means of field measurements. The opportunity of carrying out nearly monochromatic irradiance measurements offered by the UV-RAD allowed us to improve the procedure usually followed to reconstruct the solar spectrum at the surface by fitting the computed results, using radiative transfer models with field measurements of irradiance. Two long-term comparison campaigns took place, showing that a mean discrepancy of ϩ0.3% exists between the UV-RAD total ozone values and those given by the Brewer #63 spectroradiometer and that mean differences of ϩ0.3% and Ϫ0.9% exist between the erythemal dose rates determined with the UV-RAD and those obtained with the Brewer #63 and the Brewer #104 spectroradiometers, respectively.
Atmospheric Environment, 1997
ABSTRACT Continuous measurements of atmospheric CO and H2 were carried out in situ at Mt. Cimone,... more ABSTRACT Continuous measurements of atmospheric CO and H2 were carried out in situ at Mt. Cimone, northern Italy (44°12′N, 10°42′E, 2165 m a.s.l.), from May 1994 to date. The preliminary results (1994) are given in this article. Owing to the infrequent exposure to the influence of urban and industrial pollution and in spite of the continental location of the station, low CO and H2 concentrations (means of 164 for CO and of 582 ppbv for H2) were observed over most of the time. Their order of magnitude is comparable to what was found in other similar locations of the northern hemisphere, at similar latitudes. A few examples of different conditions, like pollution from the Po valley (CO increase) or transportation of air masses from the Sahara (CO decrease), are given. CO and H2 concentrations show different types of correlation with other chemical species (CO2, O3, used also as tracers) measured routinely at Mt. Cimone, as well as with meteorological and physical parameters.
Mt. Cimone, the highest peak in Italy's north-central Apennines, divides two distinct climatic re... more Mt. Cimone, the highest peak in Italy's north-central Apennines, divides two distinct climatic regions: the continentally temperate Po Valley to the north and the Mediterranean Basin to the south. It is considered a nonpolluted site, and the Italian Meteorological Service Observatory atop it, which is part of the WMO BAPMoN for the measurement of CO2, turbidity, and suspended particulate matter, has been continuously monitoring surface ozone since March 1991 together with the FISBAT Insititute. The present, preliminary study of ozone transport episodes indicates that the air masses reaching Mt. Cimone exhibit low surface-ozone concentrations under certain weather conditions, i.e. the arrival of dust-laden air from the Sahara area or in concomitance with particular low-pressure systems.
This contribution (developed within EU STACCATO project, funded by the Euro- pean Commission unde... more This contribution (developed within EU STACCATO project, funded by the Euro- pean Commission under the V Framework Programme) presents a statistical assess- ment of the stratospheric intrusions based on data recorded at a mountain station in the Italian northern Apennines. Four years (1998-2001) of surface ozone concentra- tions, Beryllium-7 concentrations and relative humidity values recorded at the Mt. Cimone research station (4411'N, 1042'E; 2165 m asl) have been analysed. More- over, the three-dimensional backward trajectories calculated by the FLEXTRA model have been considered and a dynamical description of the air masses that reached the measurement site during the events is given. In order to investigate the net contribution of the stratospheric air to the tropospheric background ozone, a "Stratospheric Intrusion Index" able to identify the stratospheric intrusion events is defined. This index has been calculated using both the data recorded at the measurement site and the potential vorticity values associated to the back- trajectories reaching Mt. Cimone. The frequency and the duration of the stratospheric intrusion episodes identified by this methodology have been evaluated, together with the mean yearly contribution of stratospheric ozone to the tropospheric ozone concen- trations recorded at Mt. Cimone.
The site of Mt. Cimone, located to the south of the Alps and the Po Valley and to the north of th... more The site of Mt. Cimone, located to the south of the Alps and the Po Valley and to the north of the Mediterranean Sea, is considered to be representative of European background conditions. At the site a number of atmospheric studies are carried out in the frame of different International Research Projects. Among these, continuous observations of climate altering gases are carried out and are here reported.
Atmospheric Environment, 2000
The study concerning carbon dioxide measurements taken during the 1997, 1998 and 1999 summer camp... more The study concerning carbon dioxide measurements taken during the 1997, 1998 and 1999 summer campaigns at two di!erent altitude stations and biospheric conditions are presented. The higher station (Mt. Cimone, 2165 m a.s.l.) is characterised by 3603 free horizon and is located on a rocky mountain while the lower (Ninfa lake, 1550 m a.s.l.) is located inside the red spruce and beech forest. The di!erent behaviour of CO at the two mountain stations has been registered. It shows the strong e!ect of nighttime soil emission and vegetation respiration on CO mixing ratio increases and of diurnal vegetative activity on CO concentration decreases at the lower measurement site. The baseline character of the higher measurement site has been con"rmed by comparison of CO diurnal amplitudes recorded at the two stations.
This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and... more This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and spatial (model grid) resolution from continuous atmospheric concentration measurements. The method is designed for regional applications and for use in intensive campaigns. We apply the method to a one month inversion of fluxes over Europe. We show that the information added by the measurements depends critically on the smoothness constraint assumed among the source components. We show that the initial condition affects the inversion for 20 days, provided one has enough observing sites to constrain regional fluxes. We show that the impact of the far-field fluxes grows throughout the inversion and hence a reasonable global flux field is a prerequisite for a regional inversion.
Atmospheric Environment, 2007
... 2003). Moreover, an additional source of pollution, including O 3 (Solberg et al., 2005), cou... more ... 2003). Moreover, an additional source of pollution, including O 3 (Solberg et al., 2005), could come from the intense fires which affected the South Europe in the considered period (Pace et al., 2005 and references therein). The ...
Atmospheric Chemistry and Physics, 2007
The CO 2 source and sink distribution across Europe can be estimated in principle through inverse... more The CO 2 source and sink distribution across Europe can be estimated in principle through inverse methods by combining CO 2 observations and atmospheric transport models. Uncertainties of such estimates are mainly due to insufficient spatiotemporal coverage of CO 2 observations and biases of the models. In order to assess the biases related to the use of different models the CO 2 concentration field over Europe has been simulated with five different Eulerian atmospheric transport models as part of the EU-funded AE-ROCARB project, which has the main goal to estimate the carbon balance of Europe. In contrast to previous comparisons, here both global coarse-resolution and regional higherresolution models are included. Continuous CO 2 observations from continental, coastal and mountain sites as well as flasks sampled on aircrafts are used to evaluate the models' ability to capture the spatiotemporal variability and distribution of lower troposphere CO 2 across Europe. 14 CO 2 is used in addition to evaluate separately fossil fuel signal predictions. The simulated concentrations show a large range of variation, with up to ∼10 ppm higher surface concentrations over Western and Central Europe in the regional models with highest (mesoscale) spatial resolution.
The CO 2 source and sink distribution across Europe can be estimated in principle through inverse... more The CO 2 source and sink distribution across Europe can be estimated in principle through inverse methods by combining CO 2 observations and atmospheric transport models. Uncertainties of such estimates are mainly due to insufficient spatiotemporal coverage of CO 2 observations and biases of the models. In order to assess the biases related to the use of different models the CO 2 concentration field over Europe has been simulated with five different Eulerian atmospheric transport models as part of the EU-funded AE-ROCARB project, which has the main goal to estimate the carbon balance of Europe. In contrast to previous comparisons, here both global coarse-resolution and regional higherresolution models are included. Continuous CO 2 observations from continental, coastal and mountain sites as well as flasks sampled on aircrafts are used to evaluate the models' ability to capture the spatiotemporal variability and distribution of lower troposphere CO 2 across Europe. 14 CO 2 is used in addition to evaluate separately fossil fuel signal predictions. The simulated concentrations show a large range of variation, with up to ∼10 ppm higher surface concentrations over Western and Central Europe in the regional models with highest (mesoscale) spatial resolution.
Atmospheric Research, 2010
The time-patterns of ground-level solar irradiance during the solar eclipse of 29 March, 2006, we... more The time-patterns of ground-level solar irradiance during the solar eclipse of 29 March, 2006, were observed at three Italian stations (Lampedusa, Mt. Cimone and Bologna) using different radiometric techniques. The global irradiance measured at the sites was found to reach the minimum at times not coinciding with those predicted by radiative transfer model evaluations, with ahead or lag times depending on the optical characteristics of the surface-atmosphere system in the areas surrounding of the stations. This different behaviour has been mainly attributed to the different influence of the environmental conditions on the diffuse radiance component measured at the observation sites. The present results indicate that the incoming diffuse radiance recorded at the three stations was appreciably affected by contributions arising from extended regions of about 30-100 km range from the stations. Such an explanation agrees very well with the theoretical evaluations obtained in earlier studies. The surrounding environmental areas of impact at ultraviolet wavelengths have been found to be wider than those in the visible and near-infrared spectral ranges.
Applied Optics, 2006
The ultraviolet narrowband filter radiometer (UV-RAD) designed by the authors to take ground-base... more The ultraviolet narrowband filter radiometer (UV-RAD) designed by the authors to take ground-based measurements of UV solar irradiance, total ozone, and biological dose rate is described, together with the main characteristics of the seven blocked filters mounted on it, all of which have full widths at half maxima that range 0.67 to 0.98 nm. We have analyzed the causes of cosine response and calibration errors carefully to define the corresponding correction terms, paying particular attention to those that are due to the spectral displacements of the filter transmittance peaks from the integer wavelength values. The influence of the ozone profile on the retrieved ozone at large solar zenith angles has also been examined by means of field measurements. The opportunity of carrying out nearly monochromatic irradiance measurements offered by the UV-RAD allowed us to improve the procedure usually followed to reconstruct the solar spectrum at the surface by fitting the computed results, using radiative transfer models with field measurements of irradiance. Two long-term comparison campaigns took place, showing that a mean discrepancy of ϩ0.3% exists between the UV-RAD total ozone values and those given by the Brewer #63 spectroradiometer and that mean differences of ϩ0.3% and Ϫ0.9% exist between the erythemal dose rates determined with the UV-RAD and those obtained with the Brewer #63 and the Brewer #104 spectroradiometers, respectively.
Atmospheric Environment, 1997
ABSTRACT Continuous measurements of atmospheric CO and H2 were carried out in situ at Mt. Cimone,... more ABSTRACT Continuous measurements of atmospheric CO and H2 were carried out in situ at Mt. Cimone, northern Italy (44°12′N, 10°42′E, 2165 m a.s.l.), from May 1994 to date. The preliminary results (1994) are given in this article. Owing to the infrequent exposure to the influence of urban and industrial pollution and in spite of the continental location of the station, low CO and H2 concentrations (means of 164 for CO and of 582 ppbv for H2) were observed over most of the time. Their order of magnitude is comparable to what was found in other similar locations of the northern hemisphere, at similar latitudes. A few examples of different conditions, like pollution from the Po valley (CO increase) or transportation of air masses from the Sahara (CO decrease), are given. CO and H2 concentrations show different types of correlation with other chemical species (CO2, O3, used also as tracers) measured routinely at Mt. Cimone, as well as with meteorological and physical parameters.
Mt. Cimone, the highest peak in Italy's north-central Apennines, divides two distinct climatic re... more Mt. Cimone, the highest peak in Italy's north-central Apennines, divides two distinct climatic regions: the continentally temperate Po Valley to the north and the Mediterranean Basin to the south. It is considered a nonpolluted site, and the Italian Meteorological Service Observatory atop it, which is part of the WMO BAPMoN for the measurement of CO2, turbidity, and suspended particulate matter, has been continuously monitoring surface ozone since March 1991 together with the FISBAT Insititute. The present, preliminary study of ozone transport episodes indicates that the air masses reaching Mt. Cimone exhibit low surface-ozone concentrations under certain weather conditions, i.e. the arrival of dust-laden air from the Sahara area or in concomitance with particular low-pressure systems.
This contribution (developed within EU STACCATO project, funded by the Euro- pean Commission unde... more This contribution (developed within EU STACCATO project, funded by the Euro- pean Commission under the V Framework Programme) presents a statistical assess- ment of the stratospheric intrusions based on data recorded at a mountain station in the Italian northern Apennines. Four years (1998-2001) of surface ozone concentra- tions, Beryllium-7 concentrations and relative humidity values recorded at the Mt. Cimone research station (4411'N, 1042'E; 2165 m asl) have been analysed. More- over, the three-dimensional backward trajectories calculated by the FLEXTRA model have been considered and a dynamical description of the air masses that reached the measurement site during the events is given. In order to investigate the net contribution of the stratospheric air to the tropospheric background ozone, a "Stratospheric Intrusion Index" able to identify the stratospheric intrusion events is defined. This index has been calculated using both the data recorded at the measurement site and the potential vorticity values associated to the back- trajectories reaching Mt. Cimone. The frequency and the duration of the stratospheric intrusion episodes identified by this methodology have been evaluated, together with the mean yearly contribution of stratospheric ozone to the tropospheric ozone concen- trations recorded at Mt. Cimone.
The site of Mt. Cimone, located to the south of the Alps and the Po Valley and to the north of th... more The site of Mt. Cimone, located to the south of the Alps and the Po Valley and to the north of the Mediterranean Sea, is considered to be representative of European background conditions. At the site a number of atmospheric studies are carried out in the frame of different International Research Projects. Among these, continuous observations of climate altering gases are carried out and are here reported.
Atmospheric Environment, 2000
The study concerning carbon dioxide measurements taken during the 1997, 1998 and 1999 summer camp... more The study concerning carbon dioxide measurements taken during the 1997, 1998 and 1999 summer campaigns at two di!erent altitude stations and biospheric conditions are presented. The higher station (Mt. Cimone, 2165 m a.s.l.) is characterised by 3603 free horizon and is located on a rocky mountain while the lower (Ninfa lake, 1550 m a.s.l.) is located inside the red spruce and beech forest. The di!erent behaviour of CO at the two mountain stations has been registered. It shows the strong e!ect of nighttime soil emission and vegetation respiration on CO mixing ratio increases and of diurnal vegetative activity on CO concentration decreases at the lower measurement site. The baseline character of the higher measurement site has been con"rmed by comparison of CO diurnal amplitudes recorded at the two stations.
This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and... more This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and spatial (model grid) resolution from continuous atmospheric concentration measurements. The method is designed for regional applications and for use in intensive campaigns. We apply the method to a one month inversion of fluxes over Europe. We show that the information added by the measurements depends critically on the smoothness constraint assumed among the source components. We show that the initial condition affects the inversion for 20 days, provided one has enough observing sites to constrain regional fluxes. We show that the impact of the far-field fluxes grows throughout the inversion and hence a reasonable global flux field is a prerequisite for a regional inversion.
Atmospheric Environment, 2007
... 2003). Moreover, an additional source of pollution, including O 3 (Solberg et al., 2005), cou... more ... 2003). Moreover, an additional source of pollution, including O 3 (Solberg et al., 2005), could come from the intense fires which affected the South Europe in the considered period (Pace et al., 2005 and references therein). The ...
Atmospheric Chemistry and Physics, 2007
The CO 2 source and sink distribution across Europe can be estimated in principle through inverse... more The CO 2 source and sink distribution across Europe can be estimated in principle through inverse methods by combining CO 2 observations and atmospheric transport models. Uncertainties of such estimates are mainly due to insufficient spatiotemporal coverage of CO 2 observations and biases of the models. In order to assess the biases related to the use of different models the CO 2 concentration field over Europe has been simulated with five different Eulerian atmospheric transport models as part of the EU-funded AE-ROCARB project, which has the main goal to estimate the carbon balance of Europe. In contrast to previous comparisons, here both global coarse-resolution and regional higherresolution models are included. Continuous CO 2 observations from continental, coastal and mountain sites as well as flasks sampled on aircrafts are used to evaluate the models' ability to capture the spatiotemporal variability and distribution of lower troposphere CO 2 across Europe. 14 CO 2 is used in addition to evaluate separately fossil fuel signal predictions. The simulated concentrations show a large range of variation, with up to ∼10 ppm higher surface concentrations over Western and Central Europe in the regional models with highest (mesoscale) spatial resolution.
The CO 2 source and sink distribution across Europe can be estimated in principle through inverse... more The CO 2 source and sink distribution across Europe can be estimated in principle through inverse methods by combining CO 2 observations and atmospheric transport models. Uncertainties of such estimates are mainly due to insufficient spatiotemporal coverage of CO 2 observations and biases of the models. In order to assess the biases related to the use of different models the CO 2 concentration field over Europe has been simulated with five different Eulerian atmospheric transport models as part of the EU-funded AE-ROCARB project, which has the main goal to estimate the carbon balance of Europe. In contrast to previous comparisons, here both global coarse-resolution and regional higherresolution models are included. Continuous CO 2 observations from continental, coastal and mountain sites as well as flasks sampled on aircrafts are used to evaluate the models' ability to capture the spatiotemporal variability and distribution of lower troposphere CO 2 across Europe. 14 CO 2 is used in addition to evaluate separately fossil fuel signal predictions. The simulated concentrations show a large range of variation, with up to ∼10 ppm higher surface concentrations over Western and Central Europe in the regional models with highest (mesoscale) spatial resolution.