Mesoscale convective systems in the Amazon basin: present climate and future projec- tions in climate change scenarios

Author(s)

Amanda Rehbein

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD)
• Defense date: 2021-04-20

Examining board members

Tercio Ambrizzi; Maria Assuncao Faus da Silva Dias; Luiz Augusto Toledo Machado; José Antonio Marengo Orsini; Meiry Sayuri Sakamoto

• Advisor: Tercio Ambrizzi

Abstract

Climate change is imminent and threatens, among others, the climate and ecosystems of the largest hydrographic basin in the world, the Amazon basin. Climatic projections estimate that precipitation in the Amazon will be drastically reduced by the end of this century. Due to the coarse resolution of these models, details on which precipitating systems and how they will be influenced are not possible to obtain. The present study investigates how the occurrence and behaviour of mesoscale convective systems (MCSs), one of the most important systems that cause precipitation in the Amazon, will be affected by climate change. Long-term simulations using a global high-resolution model, the Non-hydrostatic Icosahedral Model (NICAM), and a set of experiments and protocols, including the Coupled Model Intercomparison Project Phase 6 (CMIP6), were used in this investigation, as well as observational data from the Integrated Multi-satellitE Retrievals for GPM (IMERG), Climate Prediction Center MORPHing technique (CMORPH), Globally-merged, full-resolution IR data (MERG) among others. Characterization of the SCMs in the present climate was made, which was used in the verification of the numerical simulations. After knowing the biases of the simulations, the MCSs were investigated using future climate simulations. NICAM satisfactorily represents the occurrence and average characteristics of MCSs compared to the observations. There was a decrease in the occurrence of MCSs in the control period, which should persist in the future climate according to NICAM projections. This pattern is observed in the eastern and northern regions of the Amazon basin, mainly between October and February. On the other hand, between June and August, there was an increase in the occurrence of MCSs in the central region. MCSs precipitation contribution in the Amazon basin is 56,9% using CMORPH and 37.4% using IMERG. Numerical experiments show that the increase in spatial resolution allows a better representation of the characteristics of MCSs in the Amazon basin, but the negative bias in the north/northeast and positive bias in the south, still persist, indicating that other factors are also necessary, such as the representation of microphysics of clouds. (AU)

• FAPESP's process: 16/10557-0 - Mesoscale convective systems over the Amazon basin: present climate and future climate change scenarios
• Grantee: Amanda Rehbein
• Support Opportunities: Scholarships in Brazil - Doctorate