Monitoring Solar Radiation UV Exposure in the Comoros

Abstract

As part of the UV-Indien project, a station for measuring ultraviolet radiation and the cloud fraction was installed in December 2019 in Moroni, the capital of the Comoros, situated on the west coast of the island of Ngazidja. A ground measurement campaign was also carried out on 12 January 2020 during the ascent of Mount Karthala, located in the center of the island of Ngazidja. In addition, satellite estimates (Ozone Monitoring Instrument and TROPOspheric Monitoring Instrument) and model outputs (Copernicus Atmospheric Monitoring Service and Tropospheric Ultraviolet Model) were combined for this same region. On the one hand, these different measurements and estimates make it possible to quantify, evaluate, and monitor the health risk linked to exposure to ultraviolet radiation in this region and, on the other, they help to understand how cloud cover influences the variability of UV-radiation on the ground. The measurements of the Ozone Monitoring Instrument onboard the EOS-AURA satellite, being the longest timeseries of ultraviolet measurements available in this region, make it possible to quantify the meteorological conditions in Moroni and to show that more than 80% of the ultraviolet indices are classified as high, and that 60% of these are classified as extreme. The cloud cover measured in Moroni by an All Sky Camera was used to distinguish between the cases of UV index measurements taken under clear or cloudy sky conditions. The ground-based measurements thus made it possible to describe the variability of the diurnal cycle of the UV index and the influence of cloud cover on this parameter. They also permitted the satellite measurements and the results of the simulations to be validated. In clear sky conditions, a relative difference of between 6 and 11% was obtained between satellite or model estimates and ground measurements. The ultraviolet index measurement campaign on Mount Karthala showed maximum one-minute standard erythemal doses at 0.3 J·m−2 and very high daily cumulative erythemal doses, at more than 80 J·m−2. These very high levels are also observed throughout the year and all skin phototypes can exceed the daily erythemal dose threshold, at more than 20 J·m−2.

MAP-IO, an atmospheric and marine observatory program onboard Marion Dufresne over the Southern Ocean

“…The UV erythemal index (UV-E) measured by the SUV-E radiometer under clear sky conditions is shown in Figure 16. These conditions were identified based on cloud fraction measurements captured by the sky camera and a previously optimized cloud fraction threshold for other sites in the southwestern Indian Ocean region (Lamy et al, 2021b). A color code is utilized to signify the variable solar zenith angle.…”

Correction: Lamy et al. Monitoring Solar Radiation UV Exposure in the Comoros. Int. J. Environ. Res. Public Health 2021, 18, 10475

“…There was an error in the original article [1]. The units used for the different values of the Standard Erythemal Doses and Cumulated Standard Erythemal Doses mentioned in the Abstract, Section 3.3 and Section 4 are wrong.…”