Seminário: How ideas of chaotic mixing can advance the understanding of the South American monsoon

12/03/2021 - 14:00
Transmissão online


O seminário do Departamento de Ciências Atmosféricas será apresentado por Gabriel Perez, doutorando no Department of Meteorology, University of Reading
Resumo: The hydrological cycle in the atmosphere is highly dependent on horizontal moisture transport driven by large-scale dynamics. However, changes in dynamic aspects such as monsoons and tropical rainfall is not robust under the ongoing climate change and inconclusive in future climate simulations. This opens a window for process-based diagnostics to investigate mechanisms capable of organising moisture transport, particularly in tropical and subtropical regions. Here we employ the framework of chaotic mixing to identify Lagrangian Coherent Structures (LCSs), objective features shaping the transport of tracers in the troposphere. The aim is to unify the myriad of region and feature specific criteria typically used to identify features such as convergence zones, atmospheric rivers and low-level jets. We identify LCSs in a 30-year ERA5 dataset, showing that they frequent South America and characterise the main features associated with the South American monsoon, such as the ITCZ, the SACZ and low-level jets. Moreover, we show that intraseasonal variability changes the large-scale kinematics in order to modulate the intensity and occurrence of features such as the SACZ and fronts, thus explaining the Southeast/South Brazil rainfall dipole documented in previous climatology studies. Future plans include identifying LCSs in global climate models outputs in order to understand the challenges to simulate them in present climate as well as their sensitivity to different forcings in future climate.
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