Assessment of dry and heavy rainfall days and their projected changes over Northeast Brazil in Coupled Model Intercomparison Project Phase 6 models

Abstract

AbstractThe Northeast Brazil (NEB) is considered a region that is strongly vulnerable to extreme rainfall events due to climate change. In this context, this study evaluates the performance of 12 general circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) in representing the number of dry (DD) and heavy rainfall days (HRD) over NEB in the historical period (1981–2005) and their projections for the near (2016–2040) and far future (2076–2100) under three Shared Socioeconomic Pathways (SSP2‐4.5, SSP3‐7.0 and SSP5‐8.5) scenarios. For selection of extreme rainfall days, we used the absolute threshold of less than 1 mm for DD and the 99th percentile for HRD. The results indicate that four (three) models show an overall superior performance in reproducing the dry (heavy rainfall) days, being common in both aspects only the EC‐EARTH3. Thus, the skill of the CMIP6 models for NEB varies according to the extreme rainfall conditions analysed. For the future climate (near and far), results show that dry days are project to increase over the entire NEB territory, especially during DJF and MAM and more pronounce in the east coast, with projections that these conditions will be more severe under the SSP5‐8.5 scenario. The number of dry days may increase up to 15%. For HRD, although the results indicate that the number of days with heavy precipitation will be more frequent in the future (the increase can exceed 140%), the analysis show that under the low (SSP2‐4.5) or intermediate (SSP3‐7.0) forcing scenarios the HRD tends to be higher than in the most pessimistic scenario (SSP5‐8.5). Such result was explained according to the dryness of the atmosphere. Therefore, this study shows that it might either rain too much within a short range of time or the water scarcity will be longer‐lasting in the future in NEB.