One Year of Measurements with a POM-02 Sky Radiometer at an Alpine EuroSkyRad Station

Diémoz, Henri; Campanelli, Monica; Estellés, V.

doi:10.2151/jmsj.2014-a01

Cited by 13 publications

(11 citation statements)

References 24 publications

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“…A PM 10 comparison with the gravimetric technique was additionally performed in Aosta-Saint-Christophe and provided satisfactory results (29 d; slope 1.08±0.04; intercept −3.8±1.4 µg m −3 ; R 2 = 0.96). Further instruments to monitor trace gases (Diémoz et al, 2014b) are employed at the station and the corresponding datasets will be investigated in future studies.…”

Section: Study Region and Experimental Setupmentioning

confidence: 99%

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 2: Long-term impact on air quality

et al. 2019

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Abstract. This work evaluates the impact of trans-regional aerosol transport from the Po basin on particulate matter levels (PM10) and physico-chemical characteristics in the northwestern Alps. To this purpose, we exploited a multi-sensor, multi-platform database over a 3-year period (2015–2017) accompanied by a series of numerical simulations. The experimental setup included operational (24/7) vertically resolved aerosol profiles by an automated lidar ceilometer (ALC), vertically integrated aerosol properties by a Sun/sky photometer, and surface measurements of aerosol mass concentration, size distribution and chemical composition. This experimental set of observations was then complemented by modelling tools, including numerical weather prediction (NWP), trajectory statistical (TSM) and chemical transport (CTM) models, plus positive matrix factorisation (PMF) on both the PM10 chemical speciation analyses and particle size distributions. In a first companion study, we showed and discussed through detailed case studies the 4-D phenomenology of recurrent episodes of aerosol transport from the polluted Po basin to the northwestern Italian Alps. Here we draw more general and statistically significant conclusions on the frequency of occurrence of this phenomenon, and on the quantitative impact of this regular, wind-driven, aerosol-rich “atmospheric tide” on PM10 air-quality levels in this alpine environment. Based on an original ALC-derived classification, we found that an advected aerosol layer is observed at the receptor site (Aosta) in 93 % of days characterized by easterly winds (i.e. from the Po basin) and that the longer the time spent by air masses over the Po plain the higher this probability. Frequency of these advected aerosol layers was found to be rather stable over the seasons with about 50 % of the days affected. Duration of these advection events ranges from few hours up to several days, while aerosol layer thickness ranges from 500 up to 4000 m. Our results confirm this phenomenon to be related to non-local emissions, to act at the regional scale and to largely impact both surface levels and column-integrated aerosol properties. In Aosta, PM10 and aerosol optical depth (AOD) values increase respectively up to factors of 3.5 and 4 in dates under the Po Valley influence. Pollution transport events were also shown to modify the mean chemical composition and typical size of particles in the target region. In fact, increase in secondary species, and mainly nitrate- and sulfate-rich components, were found to be effective proxies of the advections, with the transported aerosol responsible for at least 25 % of the PM10 measured in the urban site of Aosta, and adding up to over 50 µg m−3 during specific episodes, thus exceeding alone the EU established daily limit. From a modelling point of view, our CTM simulations performed over a full year showed that the model is able to reproduce the phenomenon, but markedly underestimates its impact on PM10 levels. As a sensitivity test, we employed the ALC-derived identification of aerosol advections to re-weight the emissions from outside the boundaries of the regional domain in order to match the observed PM10 field. This simplified exercise indicated that an increase in such “external” emissions by a factor of 4 in the model is needed to halve the model PM10 maximum deviations and to significantly reduce the PM10 normalised mean bias forecasts error (from −35 % to 5 %).

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Section: Study Region and Experimental Setupmentioning

confidence: 99%

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 2: Long-term impact on air quality

et al. 2019

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“…Different products from the MERRA-2 [114] were extracted for Rome and Aosta from the Giovanni data visualization base (https://giovanni.gsfc.nasa.gov/Giovanni), for the time period 2006-2015 and used in order to understand the different roles of clouds and aerosols, i.e., the total cloud area fraction (TCAF) and the AOD at 550 nm. Although ground-based AOD is available for both stations [126,127], which would provide a more accurate climatology [128], the AOD from MERRA-2 was chosen since it was available for the whole period of study (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015). Monthly means of AOD and TCAF were downloaded and then averaged over the period 2006-2015 in order to get the monthly climatologies.…”

Section: Uv In Rome and Aostamentioning

confidence: 99%

Solar UV Irradiance in a Changing Climate: Trends in Europe and the Significance of Spectral Monitoring in Italy

et al. 2019

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Review of the existing bibliography shows that the direction and magnitude of the long-term trends of UV irradiance, and their main drivers, vary significantly throughout Europe. Analysis of total ozone and spectral UV data recorded at four European stations during 1996–2017 reveals that long-term changes in UV are mainly driven by changes in aerosols, cloudiness, and surface albedo, while changes in total ozone play a less significant role. The variability of UV irradiance is large throughout Italy due to the complex topography and large latitudinal extension of the country. Analysis of the spectral UV records of the urban site of Rome, and the alpine site of Aosta reveals that differences between the two sites follow the annual cycle of the differences in cloudiness and surface albedo. Comparisons between the noon UV index measured at the ground at the same stations and the corresponding estimates from the Deutscher Wetterdienst (DWD) forecast model and the ozone monitoring instrument (OMI)/Aura observations reveal differences of up to 6 units between individual measurements, which are likely due to the different spatial resolution of the different datasets, and average differences of 0.5–1 unit, possibly related to the use of climatological surface albedo and aerosol optical properties in the retrieval algorithms.

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“…The site is in a semirural context, partially influenced by vehicular traffic and anthropogenic activities from the city, such as domestic heating and industry. The experimental setup at this site includes an automated lidar ceilometer (ALC) for the operational monitoring of the aerosol profile (Dionisi et al, 2018), a POM-02 sun photometer for the retrieval of column aerosol properties and water vapour (Diémoz et al, 2014a;Campanelli et al, 2018), and a Fidas 200s optical particle counter (OPC) for the surface aerosol size distribution, in addition to instruments measuring solar radiation and trace gases (Diémoz et al, 2011(Diémoz et al, , 2014bSiani et al, 2013Siani et al, , 2018Federico et al, 2017). Aosta-downtown (580 m a.s.l.)…”

Section: Investigated Area and Experimental Sitesmentioning

confidence: 99%

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 1: Phenomenology

et al. 2019

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Abstract. Mountainous regions are often considered pristine environments; however they can be affected by pollutants emitted in more populated and industrialised areas, transported by regional winds. Based on experimental evidence, further supported by modelling tools, here we demonstrate and quantify the impact of air masses transported from the Po Valley, a European atmospheric pollution hotspot, to the northwestern Alps. This is achieved through a detailed investigation of the phenomenology of near-range (a few hundred kilometres), trans-regional transport, exploiting synergies of multi-sensor observations mainly focussed on particulate matter. The explored dataset includes vertically resolved data from atmospheric profiling techniques (automated lidar ceilometers, ALCs), vertically integrated aerosol properties from ground (sun photometer) and space, and in situ measurements (PM10 and PM2.5, relevant chemical analyses, and aerosol size distribution). During the frequent advection episodes from the Po basin, all the physical quantities observed by the instrumental setup are found to significantly increase: the scattering ratio from ALC reaches values >30, aerosol optical depth (AOD) triples, surface PM10 reaches concentrations >100 µg m−3 even in rural areas, and contributions to PM10 by secondary inorganic compounds such as nitrate, ammonium, and sulfate increase up to 28 %, 8 %, and 17 %, respectively. Results also indicate that the aerosol advected from the Po Valley is hygroscopic, smaller in size, and less light-absorbing compared to the aerosol type locally emitted in the northwestern Italian Alps. In this work, the phenomenon is exemplified through detailed analysis and discussion of three case studies, selected for their clarity and relevance within the wider dataset, the latter being fully exploited in a companion paper quantifying the impact of this phenomenology over the long-term (Diémoz et al., 2019). For the three case studies investigated, a high-resolution numerical weather prediction model (COSMO) and a Lagrangian tool (LAGRANTO) are employed to understand the meteorological mechanisms favouring transport and to demonstrate the Po Valley origin of the air masses. In addition, a chemical transport model (FARM) is used to further support the observations and to partition the contributions of local and non-local sources. Results show that the simulations are important to the understanding of the phenomenon under investigation. However, in quantitative terms, modelled PM10 concentrations are 4–5 times lower than the ones retrieved from the ALC and maxima are anticipated in time by 6–7 h. Underestimated concentrations are likely mainly due to deficiencies in the emission inventory and to water uptake of the advected particles not fully reproduced by FARM, while timing mismatches are likely an effect of suboptimal simulation of up-valley and down-valley winds by COSMO. The advected aerosol is shown to remarkably degrade the air quality of the Alpine region, with potential negative effects on human health, climate, and ecosystems, as well as on the touristic development of the investigated area. The findings of the present study could also help design mitigation strategies at the trans-regional scale in the Po basin and suggest an observation-based approach to evaluate the outcome of their implementation.

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One Year of Measurements with a POM-02 Sky Radiometer at an Alpine EuroSkyRad Station

Cited by 13 publications

References 24 publications

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 2: Long-term impact on air quality

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 2: Long-term impact on air quality

Solar UV Irradiance in a Changing Climate: Trends in Europe and the Significance of Spectral Monitoring in Italy

Transport of Po Valley aerosol pollution to the northwestern Alps – Part 1: Phenomenology

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