Daily Maximum Erythemal Dose Rates in the Tropics. (5th December 2018)

• Record Type: Journal Article
• Authors: Silva, Abel A.; Yamamoto, Ana L. C.; Corrêa, Marcelo P.
• Is Part Of: Photochemistry and photobiology. Volume 95:Number 3(2019)
• Page Start: 886
• Page End: 894
• Publication Date: 2018-12-05
• Subjects: Photochemistry -- Periodicals; Light -- Physiological effect -- Periodicals; 541.35
• DOI: 10.1111/php.13054
• Languages: English
• ISSNs: 0031-8655

Abstract

Abstract: The maximum erythemal dose rate (EDRmax ) at the Earth's surface tends to occur at local noon. However, clouds can make the timing of EDRmax significantly away from local noon. In fact, EDRmax and its time of occurrence depend mainly on the solar zenith angle at noon (SZAn ), site's altitude, the total ozone column (TOC), cloud cover, cloud genera and aerosols. This work depicts the daily incidence of EDRmax for Belo Horizonte (19.92°S, 43.94°W, 858 m a.s.l.) in the Southern Hemisphere tropics for a period of five years (2005–2010). Daily values of EDRmax ranged from 0.063 W m −2 (1 σ > 6.9%, Moderate UV‐Index of 3, winter) to 0.486 W m −2 (Extreme UVI of 19, summer). Indicative values of EDRmax for cloudless days were 0.336 W m −2 (summer, TOC = 258 Dobson Units), 0.311 W m −2 (fall, 260 DU), 0.253 W m −2 (spring, 274 DU) and 0.143 W m −2 (winter, 246 DU). Radiation enhancement events by clouds made EDRmax up to 45% higher than the reference EDRmax for cloudless summer skies at a time resolution of a few minutes. The main cloud genera to be associated with such events are Cumulus, Altocumulus, Altostratus and Stratocumulus. The EDR can also be significantly affected by aerosols, which attenuated on average 0.031 W m −2 (22%) of the erythemal UV in a case study at the site. Abstract : Daily maximum erythemal dose rates (EDRmax ) from November 2005 (Nov05) to September 2010 (Sep10) varying from 0.063 W m −2 (UV‐Index = 3, Moderate) in winter to 0.486 W m −2 (UVI = 19) in summer in the Southern Hemisphere tropics. Clouds are responsible for radiation enhancement events causing a surplus of up to 45% in relation to the reference EDRmax = 0.336 W m −2 for cloudless skies in summer.