The analyzed rainfall events
The rainfall during the analyzed period presented atypical seasonality
for the area, with the autumn/winter (dry session) more rainy than usual
(figure 4). The spring marked the start of the traditionally rainy
session, but the summer, usually the wettest season, did not reach the
usual rainfall levels, with less accumulated rain volume than the
winter, which was the wettest season of this hydrological year.
The analyzed events presented distinct characteristics concerning the
rainfall volume, the previous humidity conditions, and the intensity of
precipitation (Table 1). Five of the eight events analyzed presented
precipitation equal or greater than 30 mm accumulated during 24 hours,
which characterizes intense precipitation as established by Dereczynski
et al. (2009) for the city of Rio de Janeiro. The rainfall volumes
presented better adjustment to the duration of events
(r2 = 0.892; P < 0.001) than to the
intensities (r2 = 0.209; P = 0.011).
The high rainfall volume observed during winter is more associated with
the cold fronts strength than with a higher occurrence of these, with
higher rainfall volumes at each occurrence compared to what usually
occurs in other years. Thus, the autumn-winter session was characterized
by a smaller number of rainy days compared to the spring-summer session,
reflecting a trend towards a larger number of days of drought preceding
the analyzed events that occurred in autumn and winter.