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@PhDThesis{Oliveira:2019:ExTrSu,
               author = "Oliveira, J{\'e}ssica Tatiane da Silva",
                title = "Extratropical transition of subtropical cyclones over southwestern 
                         Atlantic Ocean",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2019",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2019-02-28",
             keywords = "Subtropical cyclones, extratropical transition, Potential 
                         Vorticity Inversion, ciclones subtropicais, transi{\c{c}}{\~a}o 
                         extratropical, Invers{\~a}o da Vorticidade Potencial.",
             abstract = "Subtropical cyclones that often develop over the southern coast of 
                         Brazil can significantly impact agriculture, transport and the 
                         day-to-day lives of the population. However, there is a lack of 
                         studies regarding these weather systems that is of scientific and 
                         operational interest. The goal of the current study is to improve 
                         the knowledge of the dynamical processes related to subtropical 
                         cyclones undergoing extratropical transition (SCET) and to 
                         identify the main associated mechanisms for this process. To 
                         achieve this purpose, a climatological analysis of the SCET over 
                         the Southwestern Atlantic Ocean was developed. 47 SCET were 
                         identified during the austral summer (November- March) in the 
                         1985-2015 period. An annual mean of 1.6 SCET per year with 
                         standard deviation of 1.3 was found. The monthly distribution of 
                         these systems showed that the months with higher SCET frequency 
                         were January, February and December, respectively. The main 
                         features of the structure of SCET are investigated using composite 
                         analysis of meteorological fields. The results indicate that SCET 
                         are associated with the intrusion of upper level Potential 
                         Vorticity (PV) and the propagation of cyclonic systems at the rear 
                         of the SCET. Also, the low level temperature advection plays a key 
                         role in the extratropical transition (ET) of these systems. A case 
                         study is presented to illustrate SCET pattern and investigate the 
                         impacts of PV anomalies in its life cycle. A case study was 
                         analyzed using as reference the cyclone Anita, which developed 
                         near the southeastern coast of Brazil in March 2010. The 
                         potentially significant anomalies of PV during the ET are 
                         identified through the PV inversion method. The results confirm 
                         the intrusion of an upper tropospheric PV anomaly during the 
                         pre-transitioning stage of Anita. However, the lower level PV 
                         anomalies are also found to be of great importance at the ET time. 
                         Numerical experiments with the regional model WRF (Weather 
                         Research and Forecasting) indicate that the lower level PV 
                         anomalies were fundamental to the ET of Anita. On the other hand, 
                         although the upper tropospheric PV anomaly impacts significantly 
                         the propagation and intensity of Anita, its absence did not 
                         prevent the ET occurrence. Sensitivity test suggests that the 
                         interaction of Anita with a shallow extratropical cyclone prior to 
                         the ET was not the primary mechanism to the transitioning process, 
                         but impact the time and position of its occurrence, contributing 
                         to prevent the re-intensification of Anita. RESUMO: Os ciclones 
                         subtropicais que tipicamente ocorrem nas proximidades da costa sul 
                         do Brasil impactam significativamente os meios de transporte, 
                         agricultura e o dia a dia da popula{\c{c}}{\~a}o. Apesar disso, 
                         existem poucos estudos abordando essa tem{\'a}tica de grande 
                         interesse cient{\'{\i}}fico e operacional. Este estudo visa 
                         aprimorar o conhecimento da din{\^a}mica dos ciclones 
                         subtropicais que passam por transi{\c{c}}{\~a}o extratropical 
                         (CSTE) e identificar os mecanismos fundamentais para 
                         ocorr{\^e}ncia desse processo. Para tal, uma an{\'a}lise da 
                         climatologia dos CSTE sobre o Oceano Atl{\^a}ntico Sudoeste foi 
                         elaborada. 47 CSTE foram identificados durante o ver{\~a}o 
                         austral (Novembro-Mar{\c{c}}o) durante o per{\'{\i}}odo de 
                         1985-2015. Desse modo, foi encontrada uma m{\'e}dia de 1,6 CSTE 
                         por ano, com desvio padr{\~a}o de 1,3. A distribui{\c{c}}{\~a}o 
                         mensal desses sistemas mostrou que os meses com maior 
                         freq{\"u}{\^e}ncia de CSTE foram Janeiro, Fevereiro e Dezembro, 
                         respectivamente. A estrutura dos CSTE foi investigada atrav{\'e}s 
                         da an{\'a}lise de composi{\c{c}}{\~o}es. Os resultados indicam 
                         que os CSTE est{\~a}o associados com a intrus{\~a}o de anomalia 
                         de Vorticidade Potencial (VP) de altos n{\'{\i}}veis e com a 
                         propaga{\c{c}}{\~a}o de um sistema cicl{\^o}nico na retaguarda 
                         do CSTE. Al{\'e}m disso, a advec{\c{c}}{\~a}o de temperatura na 
                         troposfera inferior desempenha um papel importante no processo de 
                         transi{\c{c}}{\~a}o extratropical (TE) desses sistemas. Um 
                         estudo de caso {\'e} apresentado para ilustrar os CSTE e para 
                         investigar os impactos das anomalias de VP durante o ciclo de vida 
                         desses sistemas. O ciclone escolhido para esse estudo de caso foi 
                         o Anita, que se desenvolveu pr{\'o}ximo a costa sudeste do Brasil 
                         em Mar{\c{c}}o de 2010. As anomalias de VP potencialmente 
                         significantes para a TE foram identificadas atrav{\'e}s do 
                         m{\'e}todo da Invers{\~a}o da Vorticidade Potencial. Os 
                         resultados confirmaram a intrus{\~a}o de uma anomalia de VP na 
                         alta troposfera durante o est{\'a}gio 
                         pr{\'e}-transi{\c{c}}{\~a}o do Anita. No entanto, as anomalias 
                         de VP de baixos n{\'{\i}}veis desempenham um papel importante 
                         durante a TE. Experimentos num{\'e}ricos com o modelo WRF 
                         (WeatherResearchandForecasting, sigla em ingl{\^e}s) indicaram 
                         que a anomalia de VP de baixos n{\'{\i}}veis {\'e} fundamental 
                         para a TE do Anita. Por outro lado, embora as anomalias de VP na 
                         alta troposfera influenciem significativamente a 
                         propaga{\c{c}}{\~a}o e intensidade do Anita, a aus{\^e}ncia 
                         delas n{\~a}o impediu a ocorr{\^e}ncia de TE. Testes de 
                         sensibilidade sugerem que a intera{\c{c}}{\~a}o do Anita com um 
                         ciclone extratropical fraco no per{\'{\i}}odo que antecede a TE, 
                         n{\~a}o foi o principal mecanismo para o processo de 
                         transi{\c{c}}{\~a}o, mas impactou o tempo e a 
                         posi{\c{c}}{\~a}o em que a transi{\c{c}}{\~a}o ocorreu, 
                         contribuindo para que a n{\~a}o re-intensifica{\c{c}}{\~a}o do 
                         Anita.",
            committee = "Gan, Manoel Alonso (presidente) and Ferreira, Nelson Jesuz 
                         (orientador) and Hodges, Kevin Ivan (orientador) and Coutinho, 
                         Mariane Mendes and Pereira Filho, Augusto Jos{\'e} and Yamazaki, 
                         Toshihiro",
         englishtitle = "Transi{\c{c}}{\~a}o extratropical de ciclones subtropicais sobre 
                         o Oceano Atl{\^a}ntico Sudoeste",
             language = "en",
                pages = "156",
                  ibi = "8JMKD3MGP3W34R/3SQM9DS",
                  url = "http://urlib.net/rep/8JMKD3MGP3W34R/3SQM9DS",
           targetfile = "publicacao.pdf",
        urlaccessdate = "28 nov. 2020"
}


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