Comparison of Ground-Based and Satellite-Derived Solar UV Index Levels at Six South African Sites

Cadet, Jean-Maurice; Benchérif, Hassan; Portafaix, Thierry; Lamy, Kévin; Ncongwane, Katlego P.; Coetzee, Gert J. R.; Wright, Caradee Y.

doi:10.3390/ijerph14111384

Cited by 26 publications

(21 citation statements)

References 25 publications

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“…201 A new dataset of UVI observations with broadband instruments at six locations in South Africa recently became available. 202 Time records at four of the six sites are as long as 21 years.…”

Section: Satellite Validationmentioning

confidence: 99%

Ozone—climate interactions and effects on solar ultraviolet radiation

Bais

Bernhard

McKenzie

et al. 2019

Photochem Photobiol Sci

139

149

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Section: Satellite Validationmentioning

confidence: 99%

Ozone—climate interactions and effects on solar ultraviolet radiation

Bais

Bernhard

McKenzie

et al. 2019

Photochem Photobiol Sci

139

149

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“…NWP (Numerical Weather Prediction) models inherently include a radiative transfer model that is used to predict GHI through a dynamic modeling of the troposphere. However, NWP models, traditionally, either neglect the presence of particles in the atmosphere or include a simplified aerosol approach (e.g., use of climatological data) resulting in large biases in solar irradiance forecasting for dust-rich environments [7,37]. In this work, we simulate GHI in Qatar and the Middle East using a regional air quality model (WRF-Chem) including a state-of-the-art prognostic treatment of aerosols [7].…”

Section: Three-dimensional Regional Air Quality Modelmentioning

confidence: 99%

“…A number of statistical tools commonly used in meteorological studies were used to validate the model. They included MBE, MAPE, RMSE, and R (Equation (5)-(8)) [7,37,50]. The statistics are defined in the next paragraph and the results are summarized in Table 2.…”

Section: Model Evaluationmentioning

confidence: 99%

UV Index Forecasting under the Influence of Desert Dust: Evaluation against Surface and Satellite-Retrieved Data

et al. 2020

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Human exposure to healthy doses of UV radiation is required for vitamin D synthesis, but exposure to excessive UV irradiance leads to several harmful impacts ranging from premature wrinkles to dangerous skin cancer. However, for countries located in the global dust belt, accurate estimation of the UV irradiance is challenging due to a strong impact of desert dust on incoming solar radiation. In this work, a UV Index forecasting capability is presented, specifically developed for dust-rich environments, that combines the use of ground-based measurements of broadband irradiances UVA (320-400 nm) and UVB (280-315 nm), NASA OMI Aura satellite-retrieved data and the meteorology-chemistry mesoscale model WRF-Chem. The forecasting ability of the model is evaluated for clear sky days as well as during the influence of dust storms in Doha, Qatar. The contribution of UV radiation to the total incoming global horizontal irradiance (GHI) ranges between 5% and 7% for UVA and 0.1% and 0.22% for UVB. The UVI forecasting performance of the model is quite encouraging with an absolute average error of less than 6% and a correlation coefficient of 0.93. In agreement with observations, the model predicts that the UV Index at local noontime can drop from 10-11 on clear sky days to approximately 6-7 during typical dusty conditions in the Arabian Peninsula-an effect similar to the presence of extensive cloud cover.Atmosphere 2020, 11, 96 2 of 17 photokeratitis (inflammation of the cornea), and suppression of the immune system [1,[3][4][5]. Thus, it is important for people to control their exposure to UV radiation [1,6].The UV radiation on the Earth's surface is largely determined by the solar zenith angle, clouds, total ozone column, surface albedo, aerosols, earth-sun distance, and altitude [7]. Clouds poorly absorb UV radiation and in general, scatter UV radiation into the atmosphere [8,9]. Stratospheric ozone (ozone layer) predominantly absorbs UV radiation at wavelengths below 320 nm [10]. The extent of reflectivity from a surface affects UV surface irradiance with higher surface albedo enhancing the net UV surface irradiance due to multiple scattering of the reflected irradiance with the atmosphere. For example, a surface covered by snow (with albedo of 0.8) will increase UV irradiance at 320 nm by 1.5 times compared to snow-free, low albedo conditions [11]. Aerosols also affect the incoming UV irradiance. They usually decrease UV irradiance reaching the surface by scattering and absorption. A measurement campaign in Greece showed that UV irradiance decreased by 5-35% due to aerosols [12], and similar numbers of annual average aerosol attenuation of UV irradiance were obtained around the globe [13]. Desert dust intrusions also affect UV irradiance with differences larger than 30% in cloudless conditions in Santiago de Chile [14,15]. These differences in UV irradiance highlight the need for ground-based measurements to account for the attenuation of UV radiation in the troposphere which are not accounted for in satellite derived es...

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“…Continuous estimates of the levels of UV irradiance at the Earth's surface on a global scale are available for the last four decades from satellite measurements [80][81][82][83]. Although in the last years there has been significant progress in the algorithms used for the retrieval of surface UV irradiance from satellites [84,85], the retrievals are still not sufficiently accurate over mountainous sites [86,87], highly reflective terrains [88], as well as over highly polluted environments [89][90][91], mainly because of the use of climatological data (for e.g., surface albedo and aerosol absorption) and simplifications in the algorithms. Furthermore, satellite retrievals represent the average of a finite area covered by the satellite pixel and are not necessarily representative for each point of the pixel, especially over complex, inhomogeneous terrains [92].…”

Section: Introductionmentioning

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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Comparison of Ground-Based and Satellite-Derived Solar UV Index Levels at Six South African Sites

Cited by 26 publications

References 25 publications

Ozone—climate interactions and effects on solar ultraviolet radiation

Ozone—climate interactions and effects on solar ultraviolet radiation

UV Index Forecasting under the Influence of Desert Dust: Evaluation against Surface and Satellite-Retrieved Data

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

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