Investigating teleconnection patterns associated with the rainy season of the northern northeast Brazil using a hidden M
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Investigating teleconnection patterns associated with the rainy season of the northern northeast Brazil using a hidden Markov model Isamara de Mendonça Silva1 · Deusdedit Monteiro Medeiros1 · Michel d. S. Mesquita2 Received: 28 February 2020 / Accepted: 9 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The interannual variability of the northern northeast Brazil (NNB) rainfall is directly affected by the dynamics of large-scale systems through atmospheric circulation. In this context, a hidden Markov model (HMM) was used to describe the daily rainfall occurrence and intensity at four meteorological stations of the Metropolitan Region of Fortaleza (MRF) in the NNB, and the global teleconnection patterns that influence precipitation regimes during the rainy season (February, March, April and May) from 1975 to 2013. An HMM with 4 states was set up and interpreted as: very rainy (1), rainy (2), less rainy (3), and dry (4) weather conditions. They agree satisfactorily with the interannual variability of the rainy season in this region. State 2 is the only one which showed a statistical trend, indicating a probable decrease of precipitation occurrence in the rainy season. Results also show that the meteorological weather associated with both states 2 and 4 is strongly related to the El Niño-Southern Oscillation (ENSO), the North Atlantic tripole and are intrinsically conditioned to the large-scale atmospheric teleconnections of the Northern Hemisphere. All those mechanisms modulate the shift of the Intertropical Convergence Zone (ITCZ) southward (state 2) or northward (state 4), thus affecting the precipitation occurrence over the NNB. State 1 is distinguished by the influence of the Atlantic Meridional Mode (AMM) and the ITCZ displacement further south, while state 3 is identified by the absence of teleconnection patterns. Keywords Hidden Markov model · Northern northeast Brazil · Rainy season · Interannual variability · Teleconnection patterns
1 Introduction One of the main characteristics of the climate in the northeast Brazil (NEB) is the large interannual variability. Climate projections for the second half of the twenty-first century show that extreme events caused by the combination of * Isamara de Mendonça Silva [email protected] Deusdedit Monteiro Medeiros [email protected] Michel d. S. Mesquita [email protected] 1
Atmospheric Research Laboratory, Postgraduate Program in Aerospace Engineering, Federal University of Rio Grande do Norte, Lagoa Nova, Natal, RN 59072‑970, Brazil
M2Lab Centre for Statistical and Data Science Research (CSDS), Norway, and 3NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Jahnebakken 5, 5007 Bergen, Norway
2
the interannual variability with climate change will affect the NEB (Marengo et al. 2017, 2018). Furthermore, increases in temperature and reductions in rainfall will be expected to be significant, indicating increased frequency and intensity of drought (Marengo et al. 2017). Yoo et al. (2015) show
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