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Agnew, Clive; Chappell, Adrian

doi:10.1023/a:1007059403077

Cited by 96 publications

(24 citation statements)

References 34 publications

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“…The Sahel is a semi-arid region with about 60 million people and encompasses West and northcentral Africa extending from Senegal eastward to Chad and Sudan (east). Although Agnew and Chappell (2) argue that the Sahel region is not well demarcated, a general geographic description of the region is that it is seated in the transitional zone between the Sahara desert to the north and the sudano and humid savannas to the south. The Sahel region analysed in this study (Longitude 10E to 20E) begins from Mali ending in Chad and covers about six semi-arid West African countries ( Fig.…”

Section: Study Regionmentioning

confidence: 99%

“…1a), including areas Agnew and Chappell (2) categorised as continental Sahel region (Mali, Burkina Faso and Niger). In the Sahelian countries, rainfall varies from less than 200 mm/year towards higher latitudes to about 400-600 mm at the southern boundary (e.g., 64,2). Annual rainfall pattern, which is regulated by the migration of the Inter-tropical Convergence Zone occurs between June and September, with maximum rainfall occurring in August.…”

Section: Study Regionmentioning

confidence: 99%

“…The use of normalised rainfall deviations in drought assessment in the Sahel has been challenged by some studies because the spatial aggregation of rainfall departures hides the underlying key local variation and drivers, and that the averaging period restricts drought characterisation and interpretation (e.g., 62,2). It is on this note that drought indicators that utilises to move towards multiple metrics to provide a more realistic profile of droughts and their drivers.…”

Section: On the Need To Optimize Drought Indicatorsmentioning

confidence: 99%

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Evolutionary drought patterns over the Sahel and their teleconnections with low frequency climate oscillations

Ndehedehe

Agutu

Ferreira

et al. 2020

Atmospheric Research

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The need for ideal drought metrics to explore the impacts of climate variability drivers on drought intensity and characteristics is essential to provide support that leads to optimizing existing templates on risk mitigation in drought-prone regions. The main aim of this study therefore is to improve contemporary understanding on the evolutionary patterns of historical drought over the Sahel (1901−2014) and the large-scale processes that drive its variability using the SPEI (standardized precipitation evapotranspiration index) and SPI (standardised precipitation index). Historically, the distributions of SPEI and SPI are generally quite similar with fairly strong correlations ranging from 0.80 to 1.0 around the central Sahel. The dissimilarity between SPI and SPEI in some regions however, suggest the influence of changing land surface conditions and the need to incorporate biophysical indicators to support the accounting process that aid the understanding of drought impacts and its cascading effects. Furthermore, SPEI and SPI confirm that the worst drought during the 20th century over the Sahel occurred between 1982 and 1985, affecting more than 90% of the region while the 1950s remained the wettest on record. However, between 2005 and 2015, drought episodes and their intensities have diminished over the Sahel. In the assessment of the coupled relationship of seven climate modes with drought evolutions, SPEI was more associated with Atlantic Multi-decadal Oscillation-AMO (r = 0.66) and Pacific Decadal Oscillation (r = −0.53) unlike the SPI. A predictive multivariate model confirms the AMO is a strong driver of drought events and in addition, highlights the multi-scale climate influence in the Sahel.

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Section: Study Regionmentioning

confidence: 99%

Section: Study Regionmentioning

confidence: 99%

Section: On the Need To Optimize Drought Indicatorsmentioning

confidence: 99%

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Evolutionary drought patterns over the Sahel and their teleconnections with low frequency climate oscillations

Ndehedehe

Agutu

Ferreira

et al. 2020

Atmospheric Research

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“…We have attempted, at the regional scale, to understand the drought frequency and trend over the region by utilizing rainfall data. Agnew and Chappell (2000) used the standardized precipitation anomaly over Burkina Faso, Mali and Niger in SSA and found evidence of negative rainfall anomalies aggregated across the region. This is coincident with our findings using hydrometeorological indices, i.e.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Comparison of trends and frequencies of drought in central North China and sub-Saharan Africa from 1901 to 2010

Ogou

Yang

et al. 2017

Atmospheric and Oceanic Science Letters

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This study compares the trends and frequencies of drought between central North China (CNC) and (SSA) for the periods 1901-2010 and 1951-2010. The Standardized Precipitation Evapotranspiration Index (SPEI) and Self-Calibrating Palmer Drought Severity Index (sc-PDSI) are used to assess the drought trends and frequencies. In general, the results exhibit downward trends of drought index values and upward trends of drought frequencies over CNC and SSA. A high rate of the trends' slopes for the drought index and a low rate of the frequencies' slopes is found over CNC with respect to SPEI and sc-PDSI. Furthermore, some abrupt changes are revealed after applying the sequential MannKendall test to detect change points. These findings offer insight into the trends and frequencies of drought over the regions studied. Further analysis needs to be undertaken to understand the mechanisms underlying the occurrence of drought in these areas.

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“…As [6] point out that not all regions of the Sahel have experienced a synchronous and systematic reduction in rainfall, and that agricultural production in the Sahelian nations has increased over the course of the period generally characterized as dry. Indeed, studies have identified different regions of coherent rainfall (seasonal variability) within the Sahelian zone, and different areas are described by different, and sometimes conflicting, anomaly patterns.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Outlines of the Rainfall Variability and the ITCZ Role over the West Sahel

Lúcio¹,

Molion²,

Valadão³

et al. 2012

ACS

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This article evaluated the plausible causes of floods and droughts, the relative roles of large-scale climate variability in regional environmental trends, and the prospects for the future of the semiarid Sahel region in the context of periodic climate change. It is pointed out that the most significant rainfall climatological changes in the Sahel probably occurred between 1950 and 1980 with the decrease of the annual rainfall, a very high deficit (about 70%) over the whole region. The last three decades considered in this research (1981-2010) showed some improvement. The more humid conditions were from the last decade 2001 to 2010. One of the most significant climatic variations has been the persistent rainfall decline in the Sahel since late 1960s. Remarkable latitudinal shift of ITF mean position towards the South generated an overall reduction of annual rainfall. Basically, in this manuscript one analyzes the dynamical features on rainfall time series and the association of the cyclic periods with teleconnections under the hypothesis that no alteration has occurred. The results supply a reliable base to develop a methodology for medium to long-term seasonal forecast

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Cited by 96 publications

References 34 publications

Evolutionary drought patterns over the Sahel and their teleconnections with low frequency climate oscillations

Evolutionary drought patterns over the Sahel and their teleconnections with low frequency climate oscillations

Comparison of trends and frequencies of drought in central North China and sub-Saharan Africa from 1901 to 2010

Dynamical Outlines of the Rainfall Variability and the ITCZ Role over the West Sahel

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