Variabilidade horo-sazonal da precipitação em Fortaleza-CE em anos de contrastes climáticos

Abstract

In this study was investigated the hourly-seasonal variability of rain in Fortaleza-CE in climatic contrasts years (of El Niño, La Niña and Normal) using thirty years (1970-2000) of five minutes rainfall rates of pluviograph data. The results suggest that the diurnal, cycle monthly average, is controlled for the effect of the terrestrial breeze, with maximum of rain in night and during dawn and the beginning of the morning, with great evidences in the years of La Niña. It occurs, independent of the composition of years, to each five minutes/day monthly, a frequency of more than 95% of not rain occurrence, with exception the years of La Niña that in the period between 21 h and 3 h was observed an inferior frequency 80%. The lesser periods of return of observed rain totals between 9-15 h, 15-21 h, 21-3 h and 3-9 h, monthly, is around 1 day for lesser rains or equal 10 mm. The measure that these totals increase the period of return grows abruptly, arriving to be bigger of three hundred days for totals above of 20 mm. The diagnosis of the configuration of rains to the long day, called rain curves, showed that it has continuous rain predominance (provoked for stratus clouds) in the composition of years of study. The exception the years of La Niña, where was observed from the 21 hours with evidence of the occurrence of convection rains (induced by cumulus clouds).