Relationship between extreme daily rainfall and temperature over the Brazilian Amazon

Abstract

Precipitation extremes will increase in most regions under warmer climates. However, the relationship between extreme rainfall intensity and atmospheric temperature is complex and depends on the physical processes responsible for generating the extreme rainfall event. While previous studies have explored this relationship, there is a limited understanding of regional variations and how methodological choices affect the observed patterns, particularly in the Brazilian Legal Amazon states. To address this gap, we analyze weather station data to investigate the relationship between daily precipitation (P) extremes and the corresponding daily temperatures (T) in this region, assessing whether differences in the P-T scaling method change this relationship’s pattern. Almost all 44 analyzed weather stations exhibited a monotonic decrease in the 99th percentile P with an increase in mean T, with the scaling exponent of-0.51 to +0.01%.°C-1. A single exception was observed when the whole year or the rainy season was considered, and five stations showed a positive scaling for the dry season. However, only half of the stations showed positive scaling when dew point temperature (DPT) was used, particularly in the eastern and southern Amazon. This suggests that the P-T relationship is influenced by moisture limitation. Nevertheless, P-T scaling using DPT was very sensitive to the bin size. These findings highlight the need for improved and integrated analysis to understand better the potential impacts of temperature increases on extreme rainfall events in the region. Several options for enhancing the analysis are discussed.