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

Environments ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 1 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Henri Diémoz ◽  
Anna-Maria Siani ◽  
Gudrun Laschewski ◽  
Gianluca Filippa ◽  
...  
Keyword(s):  
Total Ozone ◽  
Surface Albedo ◽  
Forecast Model ◽  
Urban Site ◽  
Climate Trends ◽  
Ozone Monitoring Instrument ◽  
Uv Index ◽  
Uv Irradiance ◽  
Solar Uv Irradiance

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.

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

2019 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Henri Diémoz ◽  
Annamaria Siani ◽  
Gudrun Laschewski ◽  
Gianluca Filippa ◽  
...  
Keyword(s):  
Total Ozone ◽  
Surface Albedo ◽  
Forecast Model ◽  
Urban Site ◽  
Climate Trends ◽  
Uv Index ◽  
Uv Irradiance ◽  
Country Analysis ◽  
Solar Uv Irradiance

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 DWD forecast model and 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.

scholarly journals Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

2016 ◽  
Vol 16 (4) ◽  
pp. 2493-2505 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Alkiviadis F. Bais ◽  
Konstantinos Fragkos ◽  
Charickleia Meleti ◽  
Kleareti Tourpali ◽  
...  
Keyword(s):  
Total Ozone ◽  
Single Scattering ◽  
Data Set ◽  
Uv Irradiance ◽  
Long Term Changes ◽  
Solar Uv ◽  
Short And Long Term ◽  
Solar Uv Irradiance ◽  
Sky Conditions

Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece, using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association with changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear-skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.

scholarly journals Variability and trends of the surface solar spectral ultraviolet irradiance in Italy: a possible influence of lower and upper stratospheric ozone trends

2021 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Henri Diémoz ◽  
Anna Maria Siani ◽  
Alcide di Sarra ◽  
Daniela Meloni ◽  
...  
Keyword(s):  
Total Ozone ◽  
Stratospheric Ozone ◽  
Additional Indication ◽  
Uv Irradiance ◽  
Long Term Changes ◽  
Ozone Trends ◽  
Ultraviolet Irradiance ◽  
Solar Uv Irradiance ◽  
Increasing Trends

Abstract. In this study the short- and long-term variability of the surface spectral solar ultraviolet (UV) irradiance are investigated over Italy using high quality ground based measurements from three sites located at quite different environmental conditions, and covering the full latitudinal extent of the Italian territory: Aosta (45.7° N, 7.4°  E, 570 m a.s.l.), Rome (41.9° N, 12.5° E, 75 m a.s.l.), and Lampedusa (35.5° N, 12.6° E, 50 m a.s.l.). The variability of the irradiances at 307.5 nm, 324 nm, and of the ratio between the 307.5 nm and the 324 nm irradiances were investigated with respect to the corresponding variability in total ozone and the geopotential height at 250 hPa (GPH). The study was performed for two periods: 2006–2020 for all stations, and 1996–2020 only for Rome. A statistically significant correlation between the GPH and total ozone monthly anomalies was found for all stations and all seasons of the year. A corresponding statistically significant correlation was also found in most cases between the GPH and the 307.5 nm irradiance monthly anomalies. The correlation between GPH anomalies at different sites was statistically significant, possibly explaining the strong and significant correlation between the total ozone monthly anomalies at the three sites. A statistically significant decrease of total ozone, of ~0.1 %/year was found for Rome for the period 1996–2020, which however did not induce increasing trends in irradiance at 307.5 nm (neither increasing trends in the ratio between the 307.5 nm and the 324 nm irradiances) at SZA = 67°. Further analyses revealed positive trends in the ratio and the 307.5 nm irradiance at smaller solar zenith angles (SZA), which can be attributed to the fact that total ozone decrease is driven by a decrease in the lower stratosphere while upper stratospheric ozone increases, and the effect of changes of upper stratospheric ozone becoming disproportionately larger for increasing SZA. It was also showed that long-term changes in total ozone follow changes in GPH, which is an additional indication that negative trends in total ozone are mainly driven by changes in lower stratospheric ozone. An anti-correlation between the GPH long-term changes and total ozone was also evident for all stations in 2006–2020. Positive trends in UV irradiance for this latter period which were possibly driven by changes in clouds and/or aerosols were found for Rome and Aosta. This study clearly points out the significance of dynamical processes which take place in the troposphere for the variability of total ozone and surface solar UV irradiance.

scholarly journals Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

2015 ◽  
Vol 15 (24) ◽  
pp. 35753-35785
Author(s):  
I. Fountoulakis ◽  
A. F. Bais ◽  
K. Fragkos ◽  
C. Meleti ◽  
K. Tourpali ◽  
...  
Keyword(s):  
Total Ozone ◽  
Single Scattering ◽  
Data Set ◽  
Uv Irradiance ◽  
Long Term Changes ◽  
Solar Uv ◽  
Short And Long Term ◽  
Solar Uv Irradiance ◽  
Sky Conditions

Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association to changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. Trends in irradiance during the two sub-periods are not discussed, because the length of the two datasets is too short for deriving statistically significant estimates. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.

scholarly journals Use of satellite erythemal UV products in analysing the global UV changes

2011 ◽  
Vol 11 (6) ◽  
pp. 16439-16463
Author(s):  
I. Ialongo ◽  
A. Arola ◽  
J. Kujanpää ◽  
J. Tamminen
Keyword(s):  
Uv Radiation ◽  
Total Ozone ◽  
Surface Albedo ◽  
Linear Trend ◽  
Global Scale ◽  
Ozone Monitoring Instrument ◽  
Solar Uv ◽  
Ozone Monitoring ◽  
First Time

Abstract. The amount of surface UV radiation increased during the last 30 years because of the effect of the ozone decrease (from 1979 to 1998) combined with the cloud-aerosol reflectivity changes. Long term changes in solar UV radiation affect the global biogeochemistry, climate and their interactions. During the last decades, satellite UV estimates became available for monitoring the UV level at surface from TOMS (Total Ozone Monitoring System), OMI (Ozone Monitoring Instrument) and GOME-2 (Global Ozone Monitoring Experiment-2) instruments. The combined TOMS-OMI dataset of erythemal UV products was applied for the first time to estimate the long-term UV changes at the global scale. The analysis of the uncertainty related to the different input information, is presented. OMI and GOME-2 products were compared in order to analyse the differences in the global UV distribution and their effect on the linear trend estimation. The results showed that the differences in the inputs (mainly surface albedo and aerosol information) used in the retrieval affect significantly the UV change calculation, pointing out the importance of using a consistent dataset when calculating the long term UV changes. The areas where these differences played a major role were located using global maps of monthly UV changes. Despite the uncertainties, significant positive UV changes (ranging from 0 to 6 %/decade) were observed, with higher values on the Southern Hemisphere at mid-latitudes during spring-summer, where the largest ozone decrease was observed.

scholarly journals Comparison of total ozone and erythemal UV data from OMI with ground-based measurements at Rome station

2008 ◽  
Vol 8 (1) ◽  
pp. 2381-2401 ◽  
Author(s):  
I. Ialongo ◽  
G. R. Casale ◽  
A. M. Siani
Keyword(s):  
Total Ozone ◽  
Broad Band ◽  
Urban Site ◽  
Ozone Monitoring Instrument ◽  
Dose Rates ◽  
Uv Irradiance ◽  
Daily Dose ◽  
Weighted Data ◽  
Absorbing Aerosols ◽  
Band Radiometer

Abstract. Ground-based total ozone and surface UV irradiance measurements have been collected since 1992 using Brewer spectrophotometer and Erythemal Dose Rates (EDRs) have been determined by a broad-band radiometer (model YES UVB-1) operational since 2000 at Rome station. The methodology to retrieve the EDR and the Erythemal Daily Dose (EDD) from the radiometer observations is described. Ground-based measurements were compared with satellite-derived total ozone and UV data from the Ozone Monitoring Instrument (OMI). OMI, onboard the NASA EOS Aura spacecraft, is a nadir viewing spectrometer that provides total ozone and surface UV retrievals. The results of the validation exercise showed satisfactory agreement between OMI and Brewer total ozone data, for both OMI-TOMS and OMI-DOAS ozone alghorithms (biases of −1.8% and −0.7%, respectively). Regarding UV data, OMI data overestimate ground-based erythemally weighted data retrieved from both Brewer and YES Radiometer (biases about 20%), probably because of the effect of absorbing aerosols in an urban site such as Rome.

scholarly journals Comparison of UV irradiance measurements at Summit, Greenland; Barrow, Alaska; and South Pole, Antarctica

2008 ◽  
Vol 8 (16) ◽  
pp. 4799-4810 ◽  
Author(s):  
G. Bernhard ◽  
C. R. Booth ◽  
J. C. Ehramjian
Keyword(s):  
Total Ozone ◽  
Surface Albedo ◽  
High Surface ◽  
Lower Latitude ◽  
South Pole ◽  
Model Calculations ◽  
Uv Index ◽  
Ice Caps ◽  
Clear Sky ◽  
Uv Irradiance

Abstract. An SUV-150B spectroradiometer for measuring solar ultraviolet (UV) irradiance was installed at Summit, Greenland, in August 2004. Here we compare the initial data from this new location with similar measurements from Barrow, Alaska, and South Pole. Measurements of irradiance at 345 nm performed at equivalent solar zenith angles (SZAs) are almost identical at Summit and South Pole. The good agreement can be explained with the similar location of the two sites on high-altitude ice caps with high surface albedo. Clouds attenuate irradiance at 345 nm at both sites by less than 6% on average, but can reduce irradiance at Barrow by more than 75%. Clear-sky measurements at Barrow are smaller than at Summit by 14% in spring and 36% in summer, mostly due to differences in surface albedo and altitude. Comparisons with model calculations indicate that aerosols can reduce clear-sky irradiance at Summit by 4–6%; aerosol influence is largest in April. Differences in total ozone at the three sites have a large influence on the UV Index. At South Pole, the UV Index is on average 20–80% larger during the ozone hole period than between January and March. At Summit, total ozone peaks in April and UV Indices in spring are on average 10–25% smaller than in the summer. Maximum UV Indices ever observed at Summit, Barrow, and South Pole are 6.7, 5.0, and 4.0, respectively. The larger value at Summit is due to the site's lower latitude. For comparable SZAs, average UV Indices measured during October and November at South Pole are 1.9–2.4 times larger than measurements during March and April at Summit. Average UV Indices at Summit are over 50% greater than at Barrow because of the larger cloud influence at Barrow.

scholarly journals Variability and trends in surface solar spectral ultraviolet irradiance in Italy: on the influence of geopotential height and lower-stratospheric ozone

2021 ◽  
Vol 21 (24) ◽  
pp. 18689-18705
Author(s):  
Ilias Fountoulakis ◽  
Henri Diémoz ◽  
Anna Maria Siani ◽  
Alcide di Sarra ◽  
Daniela Meloni ◽  
...  
Keyword(s):  
Geopotential Height ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Extended Period ◽  
Spectral Irradiance ◽  
Positive Trend ◽  
Uv Irradiance ◽  
Ultraviolet Irradiance ◽  
Solar Uv Irradiance

Abstract. The short- and long-term variability of the surface spectral solar ultraviolet (UV) irradiance is investigated across Italy using high-quality ground-based measurements from three locations: Aosta (45.7∘ N, 7.4∘ E, 570 m a.s.l.), Rome (41.9∘ N, 12.5∘ E, 15 75 m a.s.l.), and Lampedusa (35.5∘ N, 12.6∘ E, 50 m a.s.l.). The three sites are characterized by different environmental conditions and represent almost the full latitudinal extent of the Italian territory. Data of two periods were analysed: 2006–2020 (all sites) and 1996–2020 (Rome only). The main objective of this study is to quantify the effect of the geopotential height (GPH) at 250 hPa on total ozone, and spectral irradiance at 307.5 and 324 nm. We first show that monthly anomalies in GPH, total ozone, and spectral irradiances are correlated amongst the three sites, suggesting that Italy is often affected by the same synoptical weather systems. We further find statistically significant anticorrelations between GPH and monthly anomalies in total ozone for all stations and months. Conversely, we identify positive correlations between GPH and monthly anomalies in spectral irradiance at 307.5 nm for most months. The influence of GPH on short-term variability also hold for long-term trends. For example, long-term changes in total ozone over the period 2006–2020 were associated with changes in GPH for all stations. This suggests that observed negative trends in total ozone were mainly driven by changes in lower-stratospheric ozone as upper-stratospheric ozone was increasing over this period. For several months of the year, positive trends in UV irradiance were observed, and we found that these trends were predominantly caused by changes in clouds and/or aerosols instead of total ozone. For the longer period of 1996–2020, a statistically significant annualized decrease in total ozone of ∼ 0.1 % per year was identified for Rome and could subsequently be attributed to decreasing lower-stratospheric ozone. While positive trends in spectral irradiance at 307.5 nm were observed for several months of this extended period, the negative trend in total ozone did not lead to a positive trend in the spectral irradiance at 307.5 nm in the deseasonalized data. Our study provides evidence that dynamical processes taking place in the troposphere lead to significant variability in total ozone and surface solar UV irradiance.

scholarly journals Use of satellite erythemal UV products in analysing the global UV changes

2011 ◽  
Vol 11 (18) ◽  
pp. 9649-9658 ◽  
Author(s):  
I. Ialongo ◽  
A. Arola ◽  
J. Kujanpää ◽  
J. Tamminen
Keyword(s):  
Total Ozone ◽  
Surface Albedo ◽  
Linear Trend ◽  
Global Scale ◽  
Ozone Monitoring Instrument ◽  
Long Term Changes ◽  
Solar Uv ◽  
Ozone Monitoring ◽  
First Time

Abstract. Long term changes in solar UV radiation affect global bio-geochemistry and climate. The satellite-based dataset of TOMS (Total Ozone Monitoring System) and OMI (Ozone Monitoring Instrument) of erythemal UV product was applied for the first time to estimate the long-term ultraviolet (UV) changes at the global scale. The analysis of the uncertainty related to the different input information is presented. OMI and GOME-2 (Global Ozone Monitoring Experiment-2) products were compared in order to analyse the differences in the global UV distribution and their effect on the linear trend estimation. The results showed that the differences in the inputs (mainly surface albedo and aerosol information) used in the retrieval, affect significantly the UV change calculation, pointing out the importance of using a consistent dataset when calculating long term UV changes. The areas where these differences played a major role were identified using global maps of monthly UV changes. Despite the uncertainties, significant positive UV changes (ranging from 0 to about 5 %/decade) were observed, with higher values in the Southern Hemisphere at mid-latitudes during spring-summer, where the largest ozone decrease was observed.

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