Time-space characterization of droughts in the São Francisco river catchment using the Standard Precipitation Index and continuous wavelet transform

Abstract

This paper focuses on time-space characterization of drought conditions in the São Francisco River catchment, on the basis of wavelet analysis of Standardized Precipitation Index (SPI) time series. In order to improve SPI estimation, the procedures for regional analysis with L-moments were employed for defining statistically homogeneous regions. The continuous wavelet transform was then utilized for extracting time-frequency information from the resulting SPI time series in a multiresolution framework and for investigating possible teleconnections of these signals with those obtained from samples of the large-scale climate indexes ENSO and PDO. The use of regional frequency analysis with L-moments resulted in improvements in the estimation of SPI time series. It was observed that by aggregating regional information more reliable estimates of low frequency rainfall amounts were obtained. The wavelet analysis of climate indexes suggests that the more extreme dry periods in the study area are observed when the cold phase of both ENSO and the PDO coincides. While not constituting a strict cause effect relationship, it was clear that the more extreme droughts are consistently observed in this situation. However, further investigation is necessary for identifying particularities in rainfall patterns that are not associated to large-scale climate anomalies.

Hydrological Response to Drought Occurrences in a Brazilian Savanna Basin

“…Some researchers associate drought occurrence with anomalies in sea surface temperatures in the Pacific and the Atlantic Oceans [9,12,36]. Santos et al [41] reported that anomalies in the El Niño-Southern Oscillation (ENSO) phenomenon are related to the cycle of meteorological droughts in the region in which the PRB is located, however, the Pacific Decadal Oscillation (PDO) influence has not been identified as having a clear influence on drought events in this region. El Niño (positive phase of the ENSO) occurred during all the years in which there was a meteorological drought in the PRB, except for 2007/08 and 2016/17, when the La Niña phenomenon (negative phase of the ENSO) took place for some months.…”

Water Appropriation on the Agricultural Frontier in Western Bahia and Its Contribution to Streamflow Reduction: Revisiting the Debate in the Brazilian Cerrado

“…As widely reported in the literature [49,[60][61][62][63], the presence of STP or LTP features considerably increase the chance of type I error, leading to an overestimation of the rate of significant results in statistical hypothesis tests used to detect changes [61]. These LTP features have already been reported in the São Francisco River basin hydrologic series [15,55,64]. Additionally, the statistically-relevant results for precipitation series in the station 1344008 from 1964 to 2000, and the station 1244018 from 1936 to 2000 (Table 4), suggest the presence of subtrends that are characteristic of the existence of long-term persistence [65,66].…”

Drought Assessment in the São Francisco River Basin Using Satellite-Based and Ground-Based Indices

“…Over the past years, the SFRB has been experiencing more frequent and extreme drought events [9][10][11]. Numerous studies conducted in this basin show that the occurrence of extreme and severe meteorological drought events is linked to distinct climate systems modulated by El Niño-Southern Oscillation (ENSO) conditions [11], sea surface temperature (SST) anomalies in the tropical Atlantic [12], Pacific Decadal Oscillation (PDO) [13], or to an interaction of these indices at different time scales [10,13,14]. This situation carries serious implications for the agriculture and hydroelectric sectors, such as those observed between 2012 and 2015 [13].…”