Regionalization and spatial properties of Ceara State rainfall in northeast Brazil

The overall daily rainfall pattern of Ceara for 19 years, 1974-1992, was analyzed in terms of physiography and atmospheric circulation. This information was used to suggest a regionalization of the state's rainfall into homogeneous areas. The three large-scale precipitation mechanisms (Intertropical Convergence Zone, cold fronts, and upper air vortices) interact and create a certain rainfall pattern over the state during different months. An example of this interaction is the opposite behavior that the northern and southern parts of the state tend to have when considering the amount of precipitation during the rainy season; That is, in general, large amounts of rain in the southern part of the state tend to be associated with small amounts of rain in the northern part and vice versa, as influenced by the opposite influence of the cold fronts and the upper air vortices. At the same time, the orographical influence enhances the precipitation in the northern part of the state and decreases precipitation in the central part of the state. The state could be divided into six homogeneous precipitation regions: (1) the northwestern part of the state, locally influenced by the mountain massif of Serra da Ibiapaba; (2)-(3) the northern and northeastern Ceara influenced locally by sea breeze and the slopes of the Serra de Baturite; (4)-(5) the central state, influenced by the Chapada do Apodi and the Serra de Uruburetama; and (6) the southern part of the state, influenced mostly by cold fronts and by the slopes of the Serra do Araripe.