Influence of longer dry seasons in the Southern Amazon on patterns of water vapor transport over northern South America and the Caribbean
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Several studies have identified a recent lengthening of the dry season over the southern Amazon during the last three decades. Some explanations to this lengthening suggest the influence of changes in the regional circulation over the Atlantic and Pacific oceans, whereas others point to the influence of vegetation changes over the Amazon rainforest. This study aims to understand the implications of more frequent long dry seasons in this forest on atmospheric moisture transport toward northern South America and the Caribbean region. Using a semi-Langrangian model for water vapor tracking, results indicate that longer dry seasons in the southern Amazon relate to reductions of water vapor content over the southern and eastern Amazon basin, due to significant reductions of evaporation and recycled precipitation rates in these regions, especially during the transition from dry to wet conditions in the southern Amazon. On the other hand, longer dry seasons also relate to enhanced atmospheric moisture content over the Caribbean and northern South America regions, mainly due to increased contributions of water vapor from oceanic regions and the increase of surface moisture convergence over the equatorial region. This highlights the importance of understanding the relative role of regional circulation and local surface conditions on modulating water vapor transport toward continental regions.
KeywordsWater vapor transport Northern South America Southern Amazon dry season Water vapor tracking
This work was supported by “Departamento Administrativo de Ciencia, Tecnología e Innovación de Colombia” (Colciencias) Grant no. 115-660-44588. We acknowledge Rong Fu for her insightful comments and Nathalia Correa-Carmona for providing the data used in Fig. 2. We also thank the editor and two anonymous reviewers for helping to substantially improve this manuscript. We thank the ECMWF for providing the ERA-Interim data, as well as the Global Precipitation Climatology Project, the Climate Prediction Center, and the Center for Hydrometeorology and Remote Sensing for providing the different precipitation datasets used in this study.
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