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<p>The future behavior of synoptic-scale cyclones remains uncertain due to various factors; in terms of modeling it relies on the global climate models (GCMs) settings, such as their dynamical core, parameterizations, horizontal and vertical resolutions, etc. To cover one part of these examples, this study aims to understand how high (~ 25/50&#xa0;km) and medium (~ 50/100&#xa0;km) horizontal resolutions in HighResMIP-CMIP6 GCMs affect the climatology of cyclones over South America and southwestern South Atlantic Ocean. Present climate simulations of six GCMs are compared with CFSR and ERA5 reanalyses, the simulations reproduce the three main cyclogenetic regions near the eastern coast of South America very well. Nevertheless, high-resolution (HR) simulations slightly overestimate the frequency of cyclones compared to medium-resolution (MR) simulations. Models have smaller errors in simulating cyclone’s intensity than lifecycle, since they overestimate the long-lived events. The centered composites reveal that synoptic patterns (mean sea level pressure, 10-m winds and precipitation) of the cyclones show more organized and stronger fields in the simulations than reanalyses, especially close to the cyclone’s center. Mid-upper levels cyclogenesis mechanisms are well captured by simulations. While the differences between HR and MR composites are not visually pronounced, the Kling–Gupta efficiency (KGE) index indicates that HR performs better than MR in the representation of the cyclone spatial structures for almost all variables in all cyclogenetic regions. Although there are notable improvements in the HR simulations, synoptic-scale studies in South America using MR simulations (which are refined compared to most CMIP6 GCMs) can also be trustful.</p>

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Performance of the medium and high horizontal resolution models from HighResMIP-CMIP6 in simulating synoptic-scale cyclones over South America

  • 期刊论文

  • 发表日期：

    2025年1月11日

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  • Andressa Andrade Cardoso,
  • Rosmeri Porfírio da Rocha,
  • Michelle Simões Reboita,
  • Natália Machado Crespo,
  • Eduardo Traversi de Cai Conrado,
  • Pier Luigi Vidale

摘要

The future behavior of synoptic-scale cyclones remains uncertain due to various factors; in terms of modeling it relies on the global climate models (GCMs) settings, such as their dynamical core, parameterizations, horizontal and vertical resolutions, etc. To cover one part of these examples, this study aims to understand how high (~ 25/50 km) and medium (~ 50/100 km) horizontal resolutions in HighResMIP-CMIP6 GCMs affect the climatology of cyclones over South America and southwestern South Atlantic Ocean. Present climate simulations of six GCMs are compared with CFSR and ERA5 reanalyses, the simulations reproduce the three main cyclogenetic regions near the eastern coast of South America very well. Nevertheless, high-resolution (HR) simulations slightly overestimate the frequency of cyclones compared to medium-resolution (MR) simulations. Models have smaller errors in simulating cyclone’s intensity than lifecycle, since they overestimate the long-lived events. The centered composites reveal that synoptic patterns (mean sea level pressure, 10-m winds and precipitation) of the cyclones show more organized and stronger fields in the simulations than reanalyses, especially close to the cyclone’s center. Mid-upper levels cyclogenesis mechanisms are well captured by simulations. While the differences between HR and MR composites are not visually pronounced, the Kling–Gupta efficiency (KGE) index indicates that HR performs better than MR in the representation of the cyclone spatial structures for almost all variables in all cyclogenetic regions. Although there are notable improvements in the HR simulations, synoptic-scale studies in South America using MR simulations (which are refined compared to most CMIP6 GCMs) can also be trustful.