Daily Cycle of Precipitation over the Northern Coast of Brazil

Abstract

he daily cycle of precipitation (DCP) in the austral autumn on the northern coast of Brazil (NCB) is examined in detail. The Tropical Rainfall Measuring Mission 3B42 dataset was used to obtain the DCP, and the intradaily variability was measured using the coefficient of variation (CV). The DCP data of the NCB were grouped into five regimes. A new regime was found, called the shore regime. It has a minimum CV, and its cycle shows both continental (late afternoon peak) and oceanic features (morning peak). The landside coastal regime was divided into two areas: a continental coast regime, with very high CV, and an inland coast regime, with clear inland phase propagation. The continental regime was divided into two categories: an inland regime with low and high variability. The Forecast and Tracking of the Evolution of Cloud Clusters (ForTraCC) data were used to relate convective systems (CS) and their processes to the DCP. The following processes are studied for the CS: initiation/dissipation, merge/split, area increase/reduction, and advection. Initiation is more concentrated in time, while dissipation is more distributed. Physical mechanisms that generate initiation can promote area expansion and hence CS merge. By considering a simple parameterization, the time scale of the CS area reduction under environmental conditions that are unfavorable to initiation ranges from 6 to 12 h. Therefore, there is upscaling of the CS in the afternoon and slow decay during the night and morning, which leads to a more uniform cycle inland.