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On the impacts of tropical cyclones in the Northeastern Atlantic
Publication . Lima, Miguel Ângelo Mendes; Trigo, Ricardo Machado; Gouveia, Célia Marina Pedroso
Tropical Cyclones (TCs) are one of the most deadly and destructive weather events. Their impacts are vast and often extend beyond wind damage or storm surges. Two examples of impacts are studied in this thesis, the first relating to the interaction of TCs with the ocean, and the second showing the impact of hurricane Ophelia in the exacerbation of the 2017 Portuguese October wildfires. This work shows the average upper-ocean response, in terms of chlorophyll-a (Chl a) and sea surface temperatures (SST), the passage of a TC in the Azores region between 1998 and 2020. Significant anomalies were found on the order of +0.050 mg m−3 (Chl a) and -1.615º C (SST). Furthermore, comparing these responses with TC characteristics revealed that the TC intensity was the most critical factor. Additionally, larger TCs and those occurring later in the season also produced stronger responses, while faster TCs only had this influence with Chl a. Two case studies were conducted for hurricanes Nadine (2012) and Ophelia (2017), revealing different impacts at different stages of the TCs for both variables, additionally the importance of TC track geometry is presented. The atmospheric conditions present during hurricane Ophelia (2017) over the Iberian Peninsula were explored using the WRF-ARW regional climate model. The simulations produced a quality ensemble which represented the observed situation. These conditions were analysed by looking at the Fire Weather Index (FWI) which presented over 80 % of the territory above the 99th percentile. Comparatively the enhanced FWI (FWIe), including an atmospheric instability component, presented over 90 % of the area above the same threshold for FWIe. The role played by Ophelia was shown to be crucial for the exacerbation of the fire risk through an increase in atmospheric instability and prevalent southern circulation.
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Fundação para a Ciência e a Tecnologia

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3599-PPCDT

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PTDC/CTA-AMB/28511/2017

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