The physical hydroclimate system of the Amazon functions on several spatial and temporal scales. Large-scale processes control the main seasonal patterns of atmospheric circulation and rainfall. Seasonal variability in solar forcing, associated with the low rainforest albedo, provides energy for continental heating, convection, and the onset of the South American monsoon. Mesoscale processes cause localized circulations such as river breeze and deforestation breeze. We assessed the impact of different deforestation scenarios for the mid-century last decade rainy season. Here we describe a yet unreported synoptic-scale circulation that delays the rainy season onset in southern Amazonia. This model-predicted circulation is driven by extensive (ca. 40%) deforestation patterns and may last as long as two months. This persistent anomalous circulation may result in a rainy season onset delay of 30–40 d compared to the historical period. Like other synoptic-scale phenomena, differences in surface heating drive this circulation. Given the unabated deforestation trends, the consequences for local ecosystems, agriculture, and power generation of delayed rainy season onset associated with this circulation may be difficult to revert.

Mato Grosso (MT) state, the agricultural giant of Brazil, owes its success to the long rainy season that has allowed for the extensive adoption of double cropping, elevating the region to one of the world’s leading grain producers. However, recent studies warn of the adverse impacts of deforestation and climate variability, which are causing a decrease in rainfall and a delay in the rainy season onset. These changes pose significant threats to both ecosystems and intensive agriculture. To assess these threats, we compared past and present rainfall and rainy season duration in MT and conducted robust climate projections using climate simulations forced by realistic deforestation scenarios. Our analysis of observed rainfall data from the past four decades and Community Earth System Model simulations affirmed a worrying trend of decreasing rainfall volumes, delayed rainy season onset, and shorter rainy season length. Climate projections indicate that this pattern will intensify, with onsets expected in late October and rainy season durations shorter than 200 d by mid-century. These findings underscore the potential impact on MT’s double-cropping system, a cornerstone of the region’s agricultural success, and emphasize the urgent need for sustainable large-scale agricultural practices and strategic interventions by regional decision-makers to mitigate agricultural losses and ecosystem degradation.

Modelagem Hidrológica Combinado à Mudança Climática, Uso e Ocupação do Solo

Modelagem Hidrológica de larga escala com abordagem inercial/ Large scale Hydrological modeling with inerial approach