Assessing the representation of South American monsoon features in Brazil and U.K. climate model simulations

Abstract

This paper assesses how well the CPTEC/INPE Brazilian Global Atmospheric Model (BAM-1.2) and the atmospheric component of the UK Met Office Hadley Centre Global Environment Model (HadGEM3-GC3.1) represent the main South American monsoon features. Climatological (1981Climatological ( -2010 ensemble means of Atmospheric Model Intercomparison Project (AMIP)-type climate simulations are evaluated. The assessment evaluated the models' ability to represent the South America austral summer and winter precipitation contrast and associated circulation, key South American monsoon system elements, the association between south-east Brazil and South America precipitation, and climatological (1997/1998 to 2013/2014) distributions of rainy season onset and demise dates over south-east Brazil (15 • S-25 • S, 40 • W-50 • W) and the core monsoon region (10 • S-20 • S, 45 • W-55 • W). Despite some identified deficiencies, both models depict the monsoon region and represent the main features, including (1) the north-west-south-east precipitation band and associated ascending motion over central South America; (2) the upper-level Bolivian High and the north-east South America trough during the summer; (3) the lower-level South Atlantic and Pacific subtropical anti-cyclones and (4) the low-level jet east of the Andes. Both models represent upper-level divergence and lower-level convergence over the This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A New Look into the South America Precipitation Regimes: Observation and Forecast

“…The realistic representation of South American climate features remains a challenge for numerical models [15,[68][69][70][71][72][73][74][75]. Global climate models (GCMs) reproduce and predict the main characteristics of precipitation, temperature, and circulation over the continent.…”

“…Global climate models (GCMs) reproduce and predict the main characteristics of precipitation, temperature, and circulation over the continent. Nevertheless, they fail in simulating regional climate over terrains with a complex topography and still show systematic rainfall biases in regions such as tropical SA, Andes, and La Plata Basin (LPB) [15,[68][69][70][71][72][73][74][75]. In the SACZ region, limitations persist since summer rain predictability over the SACZ area is lower over the continent than in the ocean [76,77].…”

The climate science for service partnership Brazil

“…Much of the summer rainfall in subtropical Brazil comes from tropical regions transported Southward through cloud bands (Zilli and Hart, 2021). Understanding these dynamics enables more robust evaluation of models' dynamical fields (Coelho et al, 2022), and improved understanding of the dynamics of past drought events (Paulo et al, 2021). Ongoing research is looking at how to expand seasonal scale predictions tailored to end users such as the agricultural sector's requirement to know about dry spells and heatwaves.…”

“…Many of the impacts being felt in Brazil are related to rainfall, and so the modelling focus in CSSP Brazil has been on rainfall processes to understand near-term (seasonal) predictability as well as long-term changes. Coelho et al (2022) present an overview of seasonal and subseasonal rainfall modelling and how this has advanced bringing improved capability for early warnings. Much of the summer rainfall in subtropical Brazil comes from tropical regions transported Southward through cloud bands (Zilli and Hart, 2021).…”

A perspective for advancing climate prediction services in Brazil

“…The monsoon is one of the most important phenomena in terms of both scientific and societal interests, as a large portion of the world's population lives in regions affected by monsoon climate features. In a second climate-related CSSP-Brazil study, Coelho et al (2021b) assessed the representation of South American Monsoon features in simulations produced with the Brazilian (Coelho et al, 2021a) and UK (Ridley et al, 2018;Williams et al, 2018) global climate models. The assessment evaluated the models' ability to represent major climate features, such as the South American summer and winter precipitation contrast and associated atmospheric circulation, key elements of the South American monsoon system during spring and summer, and the climatological distributions of rainy season onset and demise dates over the core South American monsoon region.…”