Key Climate Oscillation Factors Controlling Precipitation Variability during the Dry Season in Eastern Northeast Brazil: Study Case of Mundaú and Paraíba Do Meio River Basins

Abstract

In Brazil, the northeastern region (NEB) is considered one of the most vulnerable areas of the country in terms of precipitation variability due to frequent drought episodes during the rainy season. Differently from the Northern NEB (NNEB), where dry season is consistently dry, the Eastern NEB (ENEB) exhibits a high interannual variability of precipitation during the dry season, including years exceeding 400 mm. This work aims at understanding key large-scale climate factors that modulate the high pluviometric variability of ENEB during the dry season. Multivariate statistical techniques were applied to identify the time-frequency relationship between precipitation variability and global climate phenomena. The results suggested that hydrological extreme events during the dry season became more frequent after the 1990s. Moreover, our findings also indicated a relationship, at multiannual time scales, between the state of El Niño Southern Oscillation (ENSO) and Atlantic Meridional Mode (AMM) and precipitation variability during the dry season. This additional knowledge may contribute to the formation of new perspectives of drought management, leading support to the development of a long-term drought forecasting framework, as well as to the improvement of the water resources management of the region. such as ENSO [13][14][15] and/or anomalous position or intensity of the Intertropical Convergence Zone-ITCZ due to sea surface temperature (SST) variabilities in the tropical Atlantic Ocean [8,16,17]. The NEB is exposed to different spatial-temporal rainfall regimes throughout the year. Precipitation at the Northern NEB (NNEB) is characterized by a rainy season from January to May marked by expressive interannual variability [8,16,18,19], and a dry season from June to December characterized by very low amounts of precipitation (near zero). On the other hand, Eastern NEB (ENEB) has the highest annual average precipitation of the NEB, with a wet season from March to August, is also susceptible to annual variations [20,21], but in a different way than the NNEB, while the ENEB dry season might receive substantial amount of precipitation in some years.Many studies have been conducted in order to analyze and characterize such interannual variability of precipitation in NEB, which, however, were predominantly focused on NNEB rainy season [8,10,17,[22][23][24][25][26]. There is also a growing interest in understanding the dynamics of the precipitation variability over the ENEB [18,20,[27][28][29][30]. However, most of these are focused on the rainy season of the region, its relationship with Atlantic SST patterns and the occurrence of easterly wave disturbance over the tropical Atlantic [18,19,31]. Nevertheless, the dry season in the ENEB may also exhibit high variabilities in terms of volume precipitated, as seen recently (e.g., 96 mm was precipitated in 2016-2017, and more than 400 mm in 2017-2018), and low-rainfall indices during the dry season of this region may directly impact basic economic activities (i.e., mainly rainfe...

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“…In Brazil, the northeastern region is considered the most economically vulnerable area and also one of the most susceptible to flooding episodes during the rainy season (Pereira et al, 2018). In the states of Alagoas and Pernambuco, the hydrographic basin of the Mundaú River stands out in the region.With a surface area of 4126 km 2 , 52.2% of which located in the state of Pernambuco and 47.8% in the state of Alagoas, it is the water system most used in irrigation, fishing, supply and transportation activities (Freire and Natenzon, 2019).…”