Solar erythemal irradiance in Ibarra, Ecuador (high altitude equatorial city). Ground and satellite measurements and model calculations

Abstract

The knowledge of the UV Index values, as an indicator of solar risk, allows us to adopt appropriate protection measures. This research analyzes the erythemal irradiance (directly linked with the UV Index) from July to September 2017 measured in Ibarra, Ecuador with a UV radiometer. We found that 72 days hold UVI values higher than 11 over 82 measured days, i.e. there are stages in 87.8% of the days when the UVI overcome the "extreme" value (according the WMO and WHO classification). Also, 14 days show UVI values over 20 (extremely high). Such classification doesn't seem quite adequate for this particular region. This region has important characteristics that increase the UVI: High altitude (2225 m a.s.l.), low atmospheric ozone values (248.8 }12.2 DU measured from 2005 to 2016 by OMI/NASA satellite), and great cloudiness percentage (with an annual average value of 78.5%) of "cumulus" type. This study demonstrated the need for skin protection for individuals who perform outdoor activities in Ibarra, a place considered "high risk" for skin damage progression due to its high altitude and closeness to the equator, even under cloudy skies.