Precipitation in northern Amazonia: Spatial distribution in Roraima, Brazil

Abstract

Rainfall is one of the most important variables for studies of biological processes. In the Amazon, studies of the spatial and temporal distribution of rainfall have been used as an analysis tool in regional planning aimed at the conservation of different ecosystems. This is exemplified by the construction of agricultural calendars and by controlled burning to prevent the fires that are used to clear fields and maintain pastures from escaping from control and turning into large forest fires in years of severe drought. Our study aimed to model the spatial distribution of rainfall in Brazil’s state of Roraima (1998-2018) at monthly and annual scales based on orbital data from two products available on the world-wide web (TRMM and WORLDCLIM). Ordinary kriging was adopted as a method for geostatistical modeling of precipitation considering the 59 meteorological stations located in the study area. Roraima has two well-defined climatic seasons in the year, but these seasons are inverted between the portions of the state in the northern and southern hemispheres. On average, 63.5% of the precipitation in the Af (without dry season) climate area falls between March and August, with a peak in May, while in both the Am (monsoon) and Aw (with dry winter) climates rainfall is concentrated between April and September (73% in Am and 82.3% in Aw), with the peak in June. Between 1998 and 2018 the average annual precipitation was 1925 ± 339.7 mm, regardless of the hemispheric location. Extreme climatic events have a dramatic effect on regional rainfall, where El Niño years (long droughts) are characterized as drier periods with higher risks of forest fires, while in La Niña years (wetter periods) there are higher probabilities of heavy rains associated with long periods of flooding.

Keywords:
Climate; Rainfall; Ordinary Kriging; Spatial modeling