Influence of the El Niño–Southern Oscillation and the sypnotic systems on the rainfall variability over the Brazilian Cerrado via Climate Hazard Group InfraRed Precipitation with Station data

Abstract

AbstractThe rainfall is essential to Brazil's hydrological cycle, agricultural development, and power generation, mainly Cerrado biome. Thus, the study assessed the influence of the El Niño–Southern Oscillation (ENSO) and synoptic systems on rainfall variability over the Brazilian Cerrado. To evaluate this variability, it used monthly rainfall data from the second version of the Climate Hazard Group InfraRed Precipitation with Station (CHIRPS) database (1981–2020), based on the annual densidrograms and thematic maps. In Annual terms, the average climatological was 1,417 mm·year−1. The highest precipitation values (>1,500 mm·year−1) occurred at the boundaries between Cerrado and Amazon, mainly in the states of the Maranhão, Mato Grosso, and Tocantins due to physiography (<500 m). The seasonal rainfall was more frequent in summer (on average, 48% of the annual total) distributed over the biome due to the South American monsoon system and South Atlantic convergence zone. The climatological dry period occurred between November and March (on average, 8% of the annual total) due to the Atmospheric Blocking called as Bolivia High that inhibit the passage of synoptic system transients in Central Brazil. In monthly terms, January (July) is the wetter month with 18% (drier month with 1%) of the annual total. The annual densidrograms appointed the following wetter (drier) years: 1985, 1989, and 2009 (1990, 1993, and 2012), influenced by ENSO events. The year 1985 appointed an increase of 19% in the mean annual rainfall, but in 1990 showed a reduction of 18% in climatology (1981–2020). In terms of seasonal anomalies, the summer of 1985 (1990) appointed an increase of 26% above (2.5% below) mean seasonal climatological, verified in the states of Maranhão, Piauí, and Tocantins (states of Mato Grosso). The La Niña (El Niño) events influenced positively (negatively) the annual rainfall anomalous pattern in Cerrado.Highlights The rainiest period occurs during September and April months (>200 mm·month−1). The driest period occurs during May and August months (<200 mm·month−1). 1985 (1990) year presents the most significant (smallest) annual rainfall average. The border zone between Amazon and Cerrado presents the highest annual rainfall.