Oceanic mesoscale activity influences the atmosphere in the southwestern and southern sectors of the Atlantic Ocean. However, the influence of high latitudes, specifically sea ice, on mid-latitudes and a better understanding of mesoscale ocean–atmosphere thermodynamic interactions still require further study. To quantify the effects of oceanic mesoscale activity during the periods of maximum and minimum Antarctic sea ice extent (September 2019 and February 2020), numerical experiments were conducted using a coupled regional model and an online two-dimensional spatial filter to remove high-frequency sea surface temperature (SST) oscillations. The largest SST anomalies were observed in the Brazil–Malvinas Confluence and along oceanic fronts in September, with maximum SST anomalies reaching 4.23 °C and −3.71 °C. In February, the anomalies were 2.18 °C and −3.06 °C. The influence of oceanic mesoscale activity was evident in surface atmospheric variables, with larger anomalies also observed in September. This influence led to changes in the vertical structure of the atmosphere, affecting the development of the marine atmospheric boundary layer (MABL) and influencing the free atmosphere above the MABL. Modulations in precipitation patterns were observed, not only in oceanic regions, but also in adjacent continental areas. This research provides a novel perspective on ocean–atmosphere thermodynamic coupling, highlighting the mesoscale role and importance of its representation in the study region.

The Roofline model gives insights about the performance behavior of applications bounded by either memory or processor limits, providing useful guidelines for performance improvements. This work uses the Roofline model on the analysis of the MGB model that simulates hydrological processes in largescale watersheds. Real-world input data are used to characterize the performance on two multicore architectures, one with only CPUs and one with CPUs/GPU. The MGB model performance is improved with optimizations for better memory use, and also with shared-memory (OpenMP) and GPU (OpenACC) parallelism. CPU performance achieves 42.51 % and 50.17 % of each system’s peak, whereas GPU performance is low due to overheads caused by the MGB model structure.

The dynamic load-balancing framework in Charm++/AMPI, developed at the University of Illinois, is based on using processor virtualization to allow thread migration across processors. This framework has been successfully applied to many scientific applications in the past, such as BRAMS, NAMD, ChaNGa, and others. Most of these applications use only CPUs to perform their operations. However, the use of GPUs to improve computational performance is quickly getting massively disseminated in the high-performance computing community. This paper aims to investigate how the same Charm++/AMPI framework can be extended to balance load in a synthetic application inspired by the BRAMS numerical forecast model, running mostly on GPUs rather than on CPUs. Many major questions involving the use of GPUs with AMPI where handled in this work, including: how to measure the GPU's load, how to use and share GPUs among user-level threads, and what results are obtained when applying the mandatory over-decomposition technique to a GPU-accelerated program.

The Brazilian Earth System Model (BESM) is a Global Climate Model (GCM) developed by the Brazilian National Institute for Space Research (INPE). The main purpose of a GCM is to simulate Earth’s climate in a decadal or centennial scale. The simulations usually include representations of the main elements of the Earth, such as atmosphere, ocean, ice and land. Since its first release, BESM has provided support materials for contributions to the Intergovernmental Panel on Climate Change (IPCC). This paper evaluates BESM’s performance and explores optimization possibilities, aiming to speed up the model execution. Our study started with a detailed analysis that characterized the performance of BESM executions on hundreds of processors, which served to reveal the major performance bottlenecks. Next, we worked on schemes to mitigate some of those bottlenecks. The changes made so far resulted on performance gains up to a factor of 4 in some cases, when compared to the way it was previously being executed in production. We also describe ongoing work towards additional performance improvements. Despite presenting results only for BESM, our optimization techniques are applicable to other scientific, multi-physics models as well.