Assessing the influence of intertropical discontinuity on total column ozone variation over West Africa

The focus of this study is to evaluate the influence of intertropical discontinuity (ITD) on the variation of total column ozone (TCO). Relevant information is supplied on the temporal and spatial variability of TCO along the ITD zone, which is an important factor influencing the earth's atmosphere. Several studies over the years have established the relationship and have influence several atmospheric processes on TCO. However, the relationship between intertropical discontinuity and TCO over West Africa has a gap. This study tends to examine the influence ITD has on TCO variation using the West African region as a case study. The study used wind, ozone, and dewpoint temperature data for the period between 1980 and 2019. To assess the variability and trend over the study region, several statistical methods were used, including Pearson correlation, Mann-Kendall, and linear regression model. The Mann-Kendall test shows an increasing trend throughout the months over the study region. Spatial analysis also revealed that regions north of the ITD have a higher concentration of TCO than the southern region of the ITD between April and September. However, ITD influence was more visible during the wet months of June to August (JJA) as the highest concentration of TCO was observed during this period across all latitude, but more deviation was observed between latitude 10 to 18° N, while the least occurrence is observed when ITD is at its minimum position in the month of December to February (DJF). The ACRV shows that 14° N exhibit the highest variation with a value of 4.84, while the deviation is also at its highest with value of 13.65. The monthly position of ITD for 40 years was also analysed to observe the monthly deviation along the ITD region 40 years, and the spatial distribution of TCO was analysed from January to December. It is of note that during the cause of this study, low-ozone values of 220DU are not found in the study region. The highest and the lowest value of TCO is 295 DU and 227 DU, respectively, with an average range of 68DU.

Ultraviolet light exposure, skin cancer risk and vitamin D production

The danger of overexposure to solar ultraviolet radiation has been widely reviewed since the 1980s due to the depletion of the ozone layer. However, the benefits of mild exposure of the skin to ultraviolet (UV) light have not been widely investigated. Numerous reports have demonstrated that an association exists between low light exposure to the sun, non-melanoma skin cancer and a lack of vitamin D synthesis. As vitamin D synthesis in the body depends on skin exposure to UVB radiation from the sun (wavelength, 290-320 nm), experimental measurements for this type of solar radiation are important. The present study analyzed data obtained from a laboratory investigating UV radiation from the sun at the University of Tarapacá (Arica, Chile), where systematic experimental UVB measurements had been performed using a calibrated biometer instrument since 2006. These data were compared with skin cancer data from the local population. The results demonstrated that the incidence of skin cancer systematically increased from 7.4 to 18.7 in men and from 10.0 to 21.7 in women between 2000 and 2006 in Arica, respectively; this increase may be due to multiple factors, including the lack of adequate levels of vitamin D in risk groups such as post-menopausal women and senior age. This marked increase may also be due to the high levels of UV radiation measured in this region throughout the year. However, it is not certain that the local population has adequate vitamin D levels, nor that their skin has been predominantly exposed to artificial light that does not allow adequate vitamin D synthesis. Thus, the current study presents the association between skin type IV, the time to induce solar erythema and the time required to produce 1,000 international units of vitamin D.

Monitoring of atmospheric ozone and nitrogen dioxide over the south of Portugal by ground-based and satellite observations

The SPATRAM (Spectrometer for Atmospheric TRAcers Monitoring) instrument has been developed as a result of the collaboration between CGE-UE, ISAC-CNR and Italian National Agency for New Technologies, Energy and the Environment (ENEA). SPATRAM is a multi-purpose UV-Vis-scanning spectrometer (250 - 950 nm) and it is installed at the Observatory of the CGE, in Evora, since April 2004. A brief description of the instrument is given, highlighting the technological innovations with respect to the previous version of similar equipment. The need for such measurements automatically taken on a routine basis in south-western European regions, specifically in Portugal, has encouraged the development and installation of the equipment and constitutes a major driving force for the present work. The main features and some improvements introduced in the DOAS (Differential Optical Absorption Spectroscopy) algorithms are discussed. The results obtained applying DOAS methodology to the SPATRAM spectrometer measurements of diffused spectral sky radiation are presented in terms of diurnal and seasonal variations of nitrogen dioxide (NO(2)) and ozone (O(3)). NO(2) confirms the typical seasonal cycle reaching the maximum of (6.5 +/- 0.3) x 10(+15) molecules cm(-2) for the sunset values (PM), during the summer season, and the minimum of (1.55 +/- 0.07) x 10(+15) molecules cm(-2) for the sunrise values (AM) in winter. O(3) presents the maximum total column of (433 +/- 5) Dobson Unit (DU) in the spring season and the minimum of (284 +/- 3) DU during the fall period. The huge daily variations of the O(3) total column during the spring season are analyzed and discussed. The ground-based results obtained for NO(2) and O(3) column contents are compared with data from satellite-borne equipment (GOME - Global Ozone Monitoring Experiment; SCIAMACHY - Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY; TOMS - Total Ozone Monitoring Spectrometer) and it is shown that the two data sets are in good agreement. The correlation coefficient for the comparison of the ground-based/satellite data for O(3) is of 0.97.

Sensitivity of erythemally effective UV irradiance and daily exposure to temporal variability in total ozone

The provision of information to the public about current levels of the erythemally effective UV radiation is an important issue in health care. The quality of promoted values is therefore of special importance. The atmospheric parameter which affects the erythemally effective UV radiation under clear sky most is the total ozone content of the atmosphere. In this paper we examined the sensitivity of the erythemally effective irradiance and daily radiant exposure to the temporal variability of total ozone on time scales from 1 to 15 days. The results show that the sensitivity is highest for the first 24 h. Larger time scales do not exhibit a similar influence. Total ozone measurements of the previous day may already cause uncertainties higher than 0.5 UV index (UVI) independent of the geolocation. For comparison, a temporal persistence of 15 days may cause uncertainties of 1.2 UVI at 50 degrees N, 1 UVI at 30 degrees S and less than 1 UVI at the equator. The results of this study allow finding the necessary temporal resolution of total ozone values when a certain accuracy for the UVI or for the purpose of sun protection is required. The results are compared with those of two preceding studies where we quantified the influence of measurement uncertainties and spatial total ozone variability to the erythemally effective irradiance at noon and to the daily dose. We conclude that temporal variability of total ozone is the most critical issue, but also measurement uncertainties do have a noticeable influence on the erythemally effective radiation.

Mediated modeling of the impacts of enhanced UV-B radiation on ecosystem services

This article describes the use of group model building to facilitate interaction with stakeholders, synthesize research results and assist in the development of hypotheses about climate change at the global level in relation to UV-B radiation and ecosystem service valuation. The objective was to provide a platform for integration of the various research components within a multidisciplinary research project as a basis for interaction with stakeholders with backgrounds in areas other than science. An integrated summary of the scientific findings, along with stakeholder input, was intended to produce a bridge between science and policymaking. We used a mediated modeling approach that was implemented as a pilot project in Ushuaia, Argentina. The investigation was divided into two participatory workshops: data gathering and model evaluation. Scientists and the local stakeholders supported the valuation of ecosystem services as a useful common denominator for integrating the various scientific results. The concept of economic impacts in aquatic and marsh systems was represented by values for ecosystem services altered by UV-B radiation. In addition, direct local socioeconomic impacts of enhanced UV-B radiation were modeled, using data from Ushuaia. We worked with 5 global latitudinal regions, focusing on net primary production and biomass for the marine system and on 3 plant species for the marsh system. Ecosystem service values were calculated for both sectors. The synthesis model reflects the conclusions from the literature and from experimental research at the global level. UV-B is not a significant stress for the marshes, relative to the potential impact of increases in the sea level. Enhanced UV-B favors microbial dynamics in marine systems that could cause a significant shift from primary producers to bacteria at the community level. In addition, synergetic effects of UV-B and certain pollutants potentiate the shift to heterotrophs. This may impact the oceanic carbon cycle by increasing the ratio of respiratory to photosynthetic organisms in surface waters and, thus, the role of the ocean as a carbon sink for atmospheric CO2. In summary, although changes in the marine sector due to anthropogenic influences may affect global climate change, marshes are expected to primarily be affected by climate change.

UV index experimental values during the years 2000 and 2001 from the Spanish broadband UV-B radiometric network

An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were exceptions that could be explained by cloudiness. The maximum experimental values of the UVI were around 9 during the summer, though frequently passing this value at the inland measurement stations. The annual accumulated dose of irradiation on a horizontal plane has also been studied, as well as the evolution through the year in units of energy, standard erythemal doses and minimum erythemal doses, according to different phototypes.

Comparison of column ozone retrievals by use of an UV multifilter rotating shadow-band radiometer with those from Brewer and Dobson spectrophotometers

The U.S. Department of Agriculture UV-B Monitoring Program measures ultraviolet light at seven wavelengths from 300 to 368 nm with an ultraviolet multifilter rotating shadow-band radiometer (UV-MFRSR) at 25 sites across the United States, including Mauna Loa, Hawaii. Column ozone has been retrieved under all-sky conditions near Boulder, Colorado (40.177 degrees N, 105.276 degrees W), from global irradiances of the UV-MFRSR 332- and 305-nm channels (2 nm FWHM) using lookup tables generated from a multiple-scattering radiative transfer code suitable for solar zenith angles (SZA's) up to 90 degrees. The most significant sources of error for UV-MFRSR column ozone retrievals at SZA's less than 75 degrees are the spectral characterizations of the filters and the absolute calibration uncertainty, which together yield an estimated uncertainty in ozone retrievals of +/-4.0%. Using model sensitivity studies, we determined that the retrieved column ozone is relatively insensitive (<+/-2%) to typical variations in aerosol optical depth, cloud cover, surface pressure, stratospheric temperature, and surface albedo. For 5 months in 1996-1997 the mean ratio of column ozone retrieved by the UV-MFRSR divided by that retrieved by the collocated Brewer was 1.024 and for the UV-MFRSR divided by those from a nearby Dobson was 1.025. The accuracy of the retrieval becomes unreliable at large SZA's of more than 75 degrees as the detection limit of the 305-nm channel is reached and because of overall angular response errors. The UV-MFRSR advantages of relatively low cost, unattended operation, automated calibration stability checks using Langley plots, and minimal maintenance make it a unique instrument for column ozone measurement.