Spring and summer time ozone and solar ultraviolet radiation variations over Cape Point, South Africa

Preez, David Jean du; Ajtić, Jelena; Benchérif, Hassan; Bègue, Nelson; Cadet, Jean-Maurice; Wright, Caradee Y.

doi:10.5194/angeo-37-129-2019

Cited by 7 publications

(5 citation statements)

References 47 publications

(57 reference statements)

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“…However, a recent study found that the breakup of the polar vortex had only a small effect on UV radiation at Cape Town, South Africa (34° S). Elevated levels of UV radiation at this location were more frequently associated with low-ozone air masses of tropical origin [ 234 ].…”

Section: Variability In Uv Radiation and Trends From Observationsmentioning

confidence: 99%

Stratospheric ozone, UV radiation, and climate interactions

Bernhard

Bais

Aucamp³

et al. 2023

Photochem Photobiol Sci

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This assessment provides a comprehensive update of the effects of changes in stratospheric ozone and other factors (aerosols, surface reflectivity, solar activity, and climate) on the intensity of ultraviolet (UV) radiation at the Earth’s surface. The assessment is performed in the context of the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments. Changes in UV radiation at low- and mid-latitudes (0–60°) during the last 25 years have generally been small (e.g., typically less than 4% per decade, increasing at some sites and decreasing at others) and were mostly driven by changes in cloud cover and atmospheric aerosol content, caused partly by climate change and partly by measures to control tropospheric pollution. Without the Montreal Protocol, erythemal (sunburning) UV irradiance at northern and southern latitudes of less than 50° would have increased by 10–20% between 1996 and 2020. For southern latitudes exceeding 50°, the UV Index (UVI) would have surged by between 25% (year-round at the southern tip of South America) and more than 100% (South Pole in spring). Variability of erythemal irradiance in Antarctica was very large during the last four years. In spring 2019, erythemal UV radiation was at the minimum of the historical (1991–2018) range at the South Pole, while near record-high values were observed in spring 2020, which were up to 80% above the historical mean. In the Arctic, some of the highest erythemal irradiances on record were measured in March and April 2020. For example in March 2020, the monthly average UVI over a site in the Canadian Arctic was up to 70% higher than the historical (2005–2019) average, often exceeding this mean by three standard deviations. Under the presumption that all countries will adhere to the Montreal Protocol in the future and that atmospheric aerosol concentrations remain constant, erythemal irradiance at mid-latitudes (30–60°) is projected to decrease between 2015 and 2090 by 2–5% in the north and by 4–6% in the south due to recovering ozone. Changes projected for the tropics are ≤ 3%. However, in industrial regions that are currently affected by air pollution, UV radiation will increase as measures to reduce air pollutants will gradually restore UV radiation intensities to those of a cleaner atmosphere. Since most substances controlled by the Montreal Protocol are also greenhouse gases, the phase-out of these substances may have avoided warming by 0.5–1.0 °C over mid-latitude regions of the continents, and by more than 1.0 °C in the Arctic; however, the uncertainty of these calculations is large. We also assess the effects of changes in stratospheric ozone on climate, focusing on the poleward shift of climate zones, and discuss the role of the small Antarctic ozone hole in 2019 on the devastating “Black Summer” fires in Australia. Additional topics include the assessment of advances in measuring and modeling of UV radiation; methods for determining personal UV exposure; the effect of solar radiation management (stratospheric aerosol injections) on UV radiation relevant for plants; and possible revisions to the vitamin D action spectrum, which describes the wavelength dependence of the synthesis of previtamin D3 in human skin upon exposure to UV radiation. Graphical abstract

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Section: Variability In Uv Radiation and Trends From Observationsmentioning

confidence: 99%

Stratospheric ozone, UV radiation, and climate interactions

Bernhard

Bais

Aucamp³

et al. 2023

Photochem Photobiol Sci

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“…Taking into account that there is no ground-based derived UV index for Santarém, in order to make a comparison and clarify which of the two satellite time series better represent the reality of the UVI variability in this area, the variation of the solar zenith angle (SZA) over the year for Santarém was plotted (Figure 3), so that it was possible to understand which series presents variability more in accordance with the variability of the SZA. The SZA is the angle measured from the surface between the Sun and a point directly above the observer (Du Preez, 2019;Cadet et al, 2020). Smaller SZAs results in greater solar flux reaching the Earth's surface, this happens more frequently around noon and during summer months (Wald, 2018).…”

Section: Uv Index Monthly and Seasonal Variabilitymentioning

confidence: 99%

“…Smaller SZAs results in greater solar flux reaching the Earth's surface, this happens more frequently around noon and during summer months (Wald, 2018). At larger SZAs (at dawn and dusk time), UVR is lower, as the path through the atmosphere is longer and results in more attenuation of UVR through the scattering and absorption by particles and gases in the atmosphere (Wald, 2018;Du Preez, 2019). At places within the Tropic of Capricorn the sun is at its peak twice a year and the stations register two annual maximums (Coariti, 2017).…”

Section: Uv Index Monthly and Seasonal Variabilitymentioning

confidence: 99%

UV index seasonal variability in an Amazonian city of Brazil based on satellite data

Pinheiro,

Reis,

Bencherif

et al. 2023

CeN

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The solar ultraviolet radiation - UV (280-400 nm) is a highly energetic component of the solar spectrum that needs to be monitored especially because of the effects on human health and on the ecosystems. The UV index (UVI) is a dimensionless indicator designed to report the intensity of UV incident on the Earth’s surface. It has five exposure categories, ranging from low to extreme, with recommended sun protections at each level. The higher the value, the greater the health risk. With only few stations reporting long-term ground-based UV measurements in several countries, which significantly restricts its extrapolations to all populated areas, a way for continuous monitoring UV on a global scale is through satellites. In this work, the monthly and seasonal variability of the incident UVI in Santarém, Pará, was analyzed. For this, a 13-year time series of daily UVI data from the OMI satellite instrument was used, as well as the 13-year UVI time series from the GOME-2 satellite instrument. According to the results, the dry period (July to December) shows higher average UVI than the rainy period (January to June) for the GOME-2 time series. The rainy period, on the other hand, in both series presents greater amplitude in the variability of the UVI.

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“…Clouds result in large spatial and temporal variability of surface UVR radiation levels. To remove the effect of clouds on observed UVR, clear-sky days were determined using a clear-sky determination method [42,43]. To do so, three steps were used.…”

Section: Observed Uvb Data For Pretoriamentioning

confidence: 99%

Solar Ultraviolet Radiation in Pretoria and Its Relations to Aerosols and Tropospheric Ozone during the Biomass Burning Season

et al. 2021

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Biomass burning has an impact on atmospheric composition as well as human health and wellbeing. In South Africa, the biomass burning season extends from July to October and affects the aerosol loading and tropospheric ozone concentrations which in turn impact solar ultraviolet radiation (UVR) levels at the surface. Using ground-based observations of aerosols, tropospheric ozone and solar UVR (as well as modelled solar UVR) we investigated the impact of aerosols and tropospheric ozone on solar UVR in August, September, and October over Pretoria. Aerosol optical depth (AOD) and tropospheric ozone reached a peak between September and October each year. On clear-sky days, the average relative difference between the modelled and observed solar Ultraviolet Index (UVI) levels (a standard indicator of surface UVR) at solar noon was 7%. Using modelled UVR—which included and excluded the effects of aerosols and tropospheric ozone from biomass burning—aerosols had a larger radiative effect compared to tropospheric ozone on UVI levels during the biomass burning season. Excluding only aerosols resulted in a 10% difference between the modelled and observed UVI, while excluding only tropospheric ozone resulted in a difference of −2%. Further understanding of the radiative effect of aerosols and trace gases, particularly in regions that are affected by emissions from biomass burning, is considered important for future research.

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Spring and summer time ozone and solar ultraviolet radiation variations over Cape Point, South Africa

Cited by 7 publications

References 47 publications

Stratospheric ozone, UV radiation, and climate interactions

Stratospheric ozone, UV radiation, and climate interactions

UV index seasonal variability in an Amazonian city of Brazil based on satellite data

Solar Ultraviolet Radiation in Pretoria and Its Relations to Aerosols and Tropospheric Ozone during the Biomass Burning Season

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