Mechanisms associated with large daily rainfall events in Northeast Brazil

The mechanisms resulting in large daily rainfall events in Northeast Brazil are analyzed using data filtering to exclude periods longer than 30 days. Composites of circulation fields that include all independent events do not reveal any obvious forcing mechanisms as multiple patterns contribute to Northeast Brazil precipitation variability. To isolate coherent patterns, subsets of events are selected based on anomalies that precede the Northeast Brazil precipitation events at different locations. The results indicate that at 108S, 408W, the area of lowest annual rainfall in Brazil, precipitation occurs mainly in association with trailing midlatitude synoptic wave trains originating in either hemisphere. Closer to the equator at 58S, 37.58W, an additional convection precursor is found to the west, with a spatial structure consistent with that of a Kelvin wave. Although these two sites are located within only several hundred kilometers of each other and the midlatitude patterns that induce precipitation appear to be quite similar, the dates on which large precipitation anomalies occur at each location are almost entirely independent, pointing to separate forcing mechanisms.Fil: Liebmann, Brant. National Oceanic and Atmospheric Administration. Earth System Research Laboratory; Estados UnidosFil: Kiladis, George N.. National Oceanic and Atmospheric Administration. Earth System Research Laboratory; Estados UnidosFil: Allured, Dave. National Oceanic and Atmospheric Administration. Earth System Research Laboratory; Estados UnidosFil: Vera, Carolina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Jones, Charles. University of California; Estados UnidosFil: Carvalho, Leila M. V.. University of California; Estados Unidos. Universidade de Sao Paulo; BrasilFil: Bladé, Ileana. Universidad de Barcelona; EspañaFil: Gonzalez, Paula Leticia Manuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; Argentin