Rainfall Periodicities in Amazonia

This study attempts to determine oscillations in the Amazonia rainfall at temporal scales between one day and one year. We examined records from a network of three stations. The network was designed to contrast rainfall in coastal Amazonia (Belem) with rainfall in central Amazonia (Manaus) and to observe the land/river influence on the rain (in central Amazonia). UFPa station is located on the Guama Campus of the Universidade Federal do Para, about 300 m from the northern margin of the Guama river; Careiro station, in a lowland varzea pasture on Careiro Island (near the confluence of the Amazon and Negro rivers); CEPLAC station, on the experimental field of the Brazilian Executive Commission for Cacao Production Planning (CEPLAC) (60 km northwest of the city of Manaus). The experimental field of cacao trees at CEPLAC is surrounded by "terra firme" rain forest. The analysis was conducted at hourly resolution for the three year period beginning in I January 1988. The results of this analysis are first presented for Careiro rainfall records and later compared with rainfall oscillations obtained at the other locations. To the extent that rainfall in eastern Amazonia originates in deep convective clouds, the results may help to understand the periodic behavior of lightning.