Cloud enhancement occurrences analysis in Afogados da Ingazeira city in Brazilian northeast

摘要

The ground irradiance has a physical limit plenty known as extraterrestrial irradiance, but recent researches relate that this physical limit can be overcome when a cloud edge or cloud enhancement effect happens. Values around 1800 W/m~2 are reported and assigned to this effect. This work presents a cloud enhancement occurrence analysis in Afogados da Ingazeira city, located in arid region of Brazilian northeast using three years of minute irradiance data. An algorithm was developed to identify and classify the overirradiance duration. The monthly occurrences frequencies of this effect were analyzed, and it was observed that in the period from May to September there is a higher frequency occurrence and from October to December there is a lower frequency of occurrences. Related to length of time, it was developed an algorithm to identify and group sequences of time. Fast events are most frequent than slow ones, as indicated in literature. The hourly distribution pointed that the occurrences frequency increases in the morning and decreases in the afternoon. The highest value measured was 1571 W/m~2 and the largest duration was 12 minutes.