Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 7671-7681, 2017
https://doi.org/10.5194/acp-17-7671-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
26 Jun 2017
Meteorological context of the onset and end of the rainy season in Central Amazonia during the GoAmazon2014/5
Jose A. Marengo1, Gilberto F. Fisch2, Lincoln M. Alves3, Natanael V. Sousa3, Rong Fu4, and Yizhou Zhuang4,5 1Centro Nacional de Monitoramento e Alerta de Desastres Naturais (CEMADEN), São Jose dos Campos, São Paulo, Brazil
2Instituto de Aeronáutica e Espaço/Centro Tecnológico Aeroespacial (IAE/CTA), São Jose dos Campos, São Paulo, Brazil
3Centro de Ciência do Sistema Terrestre/Instituto Nacional de Pesquisas Espaciais (CCST INPE), São Jose dos Campos, São Paulo, Brazil
4Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA
5Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
Abstract. The onset and demise of the rainy season in Amazonia are assessed in this study using meteorological data from the GoAmazon experiment, with a focus on the 2014–2015 rainy season. In addition, global reanalyses are also used to identify changes in circulation leading to the establishment of the rainy season in the region. Our results show that the onset occurred in January 2015, 2–3 pentads later than normal, and the rainy season during the austral summer of 2015 contained several periods with consecutive dry days in both Manacapuru and Manaus, which are not common for the wet season, and resulted in below-normal precipitation. The onset of the rainy season has been strongly associated with changes in large-scale weather conditions in the region due to the effect of the Madden–Julian Oscillation (MJO). Regional thermodynamic indices and the height of the boundary layer did not present a significant difference between the onset and demise of the wet season of 2015. This suggests that local changes, such as those in the regional thermodynamic characteristics, may not have influenced its onset. Thus, variability of the large-scale circulation was responsible for regional convection and rainfall changes in Amazonia during the austral summer of 2014–2015.

Citation: Marengo, J. A., Fisch, G. F., Alves, L. M., Sousa, N. V., Fu, R., and Zhuang, Y.: Meteorological context of the onset and end of the rainy season in Central Amazonia during the GoAmazon2014/5, Atmos. Chem. Phys., 17, 7671-7681, https://doi.org/10.5194/acp-17-7671-2017, 2017.
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Short summary
The onset and demise of the rainy season in Amazonia are assessed in this study using meteorological data from the GoAmazon experiment for the 2014–15 rainy season. The onset of the rainy season was strongly associated with changes in large-scale circulation in the region, and our analyses using regional thermodynamic indices suggest that local changes such the regional thermodynamic characteristics may have been less important on the occurrence of the onset compared to large-scale circulation.
The onset and demise of the rainy season in Amazonia are assessed in this study using...
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