Overirradiance: Caracterization and Forecast in the Central Amazon
Abstract
In this study, we present some aspects related with the relationship between overirradiance, short-term irradiance variability and cloud cover in Central Amazonia. The analysis focuses on how cloud morphology and atmospheric conditions modulate the temporal structure of surface solar irradiance. Results show a positive correlation (r = 0.63) was found between DARR and overirradiance frequency, stronger during the wet season (r = 0.67) than the dry season (r = 0.58), reflecting the role of fragmented cloud fields and optical properties in enhancing rapid fluctuations. Intraday variability peaks around local noon, particularly in the afternoon, indicating higher susceptibility to sharp irradiance ramps during this period. Cloud type analysis shows that low clouds dominate overirradiance events, while _cirrus_ and _altocumulus_ also increase in frequency, though with lower optical efficiency. _Cumulus congestus_ and low clouds produce the most intense ramps, whereas _cirrus_ generate lower but still significant fluctuations. These results highlight the influence of cloud morphology on the temporal structure of solar irradiance and provide a physical basis to support very short-term forecasting approaches, as discussed in Rocha et al. (2025) e Rocha (2025).
Keywords
surface solar irradiance, cloud enhancement, solar variability, cloud types, GHI, prediction