Monitoring Rainfall Patterns in the Southern Amazon with PERSIANN-CDR Data: Long-Term Characteristics and Trends

Abstract

Satellite-derived estimates of precipitation are essential to compensate for missing rainfall measurements in regions where the homogeneous and continuous monitoring of rainfall remains challenging due to low density rain gauge networks. The Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) is a relatively new product (released in 2013) but that contains data since 1983, thus enabling long-term rainfall analysis. In this work, we used three decades (1983-2014) of PERSIANN-CDR daily rainfall data to characterize precipitation patterns in the southern part of the Amazon basin, which has been drastically impacted in recent decades by anthropogenic activities that exacerbate the spatio-temporal variability of rainfall regimes. We computed metrics for the rainy season (onset date, demise date and duration) on a pixel-to-pixel basis for each year in the time series. We identified significant trends toward a shortening of the rainy season in the southern Amazon, mainly linked to earlier demise dates. This work thus contributes to monitoring possible signs of climate change in the region and to assessing uncertainties in rainfall trends and their potential impacts on human activities and natural ecosystems.

Climate change evidence in Brazil from Köppen's climate annual types frequency

“…The maps in Figure provide a synthetic measure of the shifts of the regional frequency of the main ACT large classes (A, B, C) by representing their respective percentages for each period. These maps confirm that humid tropical climates (cumulating Af and Am) have declined sharply in the western central part of the country and the southern Amazon, confirming the decrease in precipitation observed in this region by various authors (Marengo, ; Dubreuil et al ., ; Fu et al ., ; Debortoli et al ., ; Almeida et al ., ; Arvor et al ., ; Khanna et al ., ): in Porto Velho, for example (Figure ‐3) the Am type represented only a third of the ACT observed during the recent period. In the northeast of Brazil, the extension of the frequencies of “B” types confirms the increasing aridity of the interior of the Bahia to the coastline of Ceará (Lacerda et al ., ; Marengo et al ., ).…”

The southern Amazon rainy season: The role of deforestation and its interactions with large‐scale mechanisms

“…They indicate a reduction of the rainy season that is more linked to early demise, mainly in Rondônia and western Mato Grosso, rather than to a delayed onset of the rainy season only observed in Bolivia. Although this trend's opposition between Bolivia and Mato Grosso found by Arvor et al (2017) are intriguing, we cannot repeat our analysis for Bolivia due to the lack of equivalent historical land use series.…”

“…However, removing 1998/99 in the duration trend (Figure 3c), a large difference exists ( L t = −0.04t + 243.27; r 2 = 0.002, p = .5) and statistical trends differ between analyses including versus excluding this outlier. Arvor et al (2017) demonstrated a strong heterogeneity of rainfall trends at a regional level in the southern Amazon. They indicate a reduction of the rainy season that is more linked to early demise, mainly in Rondônia and western Mato Grosso, rather than to a delayed onset of the rainy season only observed in Bolivia.…”

Addendum: Arvor, D. et al. Monitoring Rainfall Patterns in the Southern Amazon with PERSIANN-CDR Data: Long-Term Characteristics and Trends. Remote Sens. 2017, 9, 889

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After publication of the paper [1] it was found that the Acknowledgments section did not mention the institutions that supported this research. This work was supported by (1) Rennes Métropole, who funded an "Allocation d'Installation Scientifique", and (2) the European Union, which funded the H2020-MSCA-RISE-2015 ODYSSEA project (Project Reference: 691053).

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