Thesis defense
Student: Isaque Saes Lanfredi
Program: Meteorology
Title: “ HEAT WAVES AS A FUNCTION OF THE MULTI-SCALE COMBINATION OF THE METEOROLOGICAL SYSTEMS INVOLVED: A GLOBAL STUDY WITH EMPHASIS ON SOUTH AMERICA"
Advisor: Prof. Dr. Ricardo de Camargo - IAG/USP
Judging Committee:
- Prof. Dr. Ricardo de Camargo – Presidente e Orientador
- Prof. Dr. Pedro Leite da Silva Dias - IAG/USP (por videoconferência)
- Dra. Mary Toshie Kayano – INPE (por videoconferência)
- Profa. Dra. Matilde Monica Rusticucci - UBA (por videoconferência)
- Prof. Dr. José Maria Brabo Alves – UECE (por videoconferência)
Abstract:
Heatwaves are prolonged periods of high temperatures that can potentially produce economic, biological, and social impacts. Accordingly, the literature includes numerous studies encompassing a wide spatiotemporal scale of the meteorological systems involved, ranging from synoptic analyses of specific cases to the investigation of disturbances linked to low-frequency dynamics. In fact, during a low-frequency disturbance that favors above-average temperatures, a higher-frequency disturbance may sometimes enhance its effects, forming the heatwaves. In this context, this thesis aims to study heatwaves from a multi-scale perspective, focusing on the combined influence of meteorological systems acting at different scales. To this end, the study analyzes these phenomena at each grid point within the global domain using reanalysis data, as well as through the identification of homogeneous regions of high temperatures that highlight the distinct areas where heatwaves occur and their specific characteristics. The first step involves identifying homogeneous regions using correlations in a novel methodology analogous to the teleconnectivity maps, but adapted for high temperatures. This is followed by validation through a Hierarchical Cluster Analysis, also adapted for this specific purpose. Heatwaves are then characterized through statistical analyses of the identified phenomena in the spatiotemporal domain, as well as through mean and anomaly composites of meteorological fields for the days included in the heatwaves. The thesis then applies the methodologies developed thus far to regional studies focused on South America, divided into two parts: one addressing the heatwave that occurred in April 2016 across much of Brazil, analyzed within the climatological context of global teleconnections using Influence Functions; the other contextualizing heatwaves over northern Amazonas, using Granger Causality analysis between time series. The case study results suggest that the April 2016 event is representative of the climatology of heatwaves in the affected region, potentially favored by El Niño, atmospheric blocking over the southeastern Pacific, and the Madden-Julian Oscillation in phases 3 to 6. High temperatures over northern Amazonas are directly or indirectly related to the Niño Oceanic Index, Pacific South American (PSA) pattern, North Atlantic Oscillation, Madden-Julian Oscillation, and the Atlantic Meridional Mode (TASI index). El Niño, in conjunction with the PSA and elevated temperatures in the North Atlantic, constitutes the primary mode of variability for this region.
Keywords: Heatwaves, teleconnections, Influence Functions, Granger Causality