The recent trend of increasing precipitation in Sahel and the associated inter‐hemispheric dipole of global SST

Munemoto, Masaki; Tachibana, Yukio

doi:10.1002/joc.2356

Cited by 19 publications

(24 citation statements)

References 12 publications

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“…Although there is no visible evidence of change, it is conceivable that the SST time series has a changing phase from 1984 using the SST over the Northern Hemisphere (NH) and SH. As demonstrated by Munemoto and Tachibana (2012), the NH SST became lower than that of the SH SST and described an opposite trend after 1984. Figure 4 shows that areas of positive trend shift in the JAS SST over the oceans are widespread in the NH, meaning that SST decreased until 1984 and then increased.…”

Section: Global Sst Trend Shiftmentioning

confidence: 93%

“…Sahel rainfall decreased from the early 1960s to the mid1980s, followed by an increasing trend for the rest of the study period. The driest year of the study period was 1984 (Munemoto and Tachibana, 2012); we focused on that period to divide our data set into two different periods, the decreasing and increasing periods. The mid-1980s mark a clear reversal in these multi-decadal trends.…”

Section: Methodsmentioning

confidence: 99%

“…Sahel rainfall is related to nearby SST (Lough, 1986;Bader and Latif, 2003;Chung and Ramanathan, 2006) and remote SST (Folland et al, 1986;Janicot et al, 1996;Rowell, 2003;Fontaine et al, 2011;Munemoto and Tachibana, 2012;Diatta and Fink, 2014). Although there is no visible evidence of change, it is conceivable that the SST time series has a changing phase from 1984 using the SST over the Northern Hemisphere (NH) and SH.…”

Section: Global Sst Trend Shiftmentioning

confidence: 99%

“…Pomposi et al (2015) examined the role of global SST anomalies and their effects on monsoon variability in the Sahel region and found that "much of the internal variability of the global monsoon system" is generated by SST variances and their outcome on the atmospheric teleconnections, linking oceanic variations to land-based rainfall. Munemoto and Tachibana (2012) demonstrated that the contrast between northern and southern SST also corresponds to the more recent pattern of Sahel rainfall; in the mid-1980s, the phenomenon shifted from a decreasing trend to an increasing trend. These various studies underscore the lack of a single mechanism determining the relationship between the shift of the Sahel rainfall and the shift of oceanic evaporation.…”

Section: Introductionmentioning

confidence: 97%

“…Other studies related to remote SST point out that the precipitation time's series have considerably changed over the past 60 years as well (Folland et al, 1986;Janicot et al, 1996;Rowell, 2003;Fontaine et al, 2011;Munemoto and Tachibana, 2012;Diatta and Fink, 2014). The potential long-term causes and effects of SST variability are important inputs for the thermodynamical process of Sahel rainfall (Folland et al, 1986;Giannini et al, 2003;Tippett and Giannini, 2006;Lu and Delworth, 2005;Hoerling et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Synchrony of trend shifts in Sahel boreal summer rainfall and global oceanic evaporation, 1950–2012

Diawara

Tachibana

Oshima

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Between 1950 and 2012, boreal summer (rainy season) rainfall in the Sahel changed from a multi-decadal decreasing trend to an increasing trend (positive trend shift) in the mid-1980s. We found that this trend shift was synchronous with similar trend shifts in global oceanic evaporation and in land precipitation on all continents except the Americas. The trend shift in oceanic evaporation occurred mainly in the Southern Hemisphere (SH) and the subtropical oceans of the Northern Hemisphere (NH). Because increased oceanic evaporation strengthens the atmospheric moisture transport toward land areas, the synchrony of oceanic evaporation and land precipitation is reasonable. Surface scalar winds over the SH oceans also displayed a positive trend shift. Sea surface temperature (SST) displayed a trend shift in the mid-1980s that was negative (increasing, then decreasing) in the SH and positive in the NH. Although SST had opposite trend shifts in both hemispheres, the trend shift in evaporation was positive in both hemispheres. We infer that because strong winds promote evaporative cooling, the trend shift in SH winds strengthened the trend shifts in both SST and evaporation in the SH. Because high SST promotes evaporation, the trend shift in NH SST strengthened the NH trend shift in evaporation. Thus differing oceanic roles in the SH and NH generated the positive trend shift in evaporation; however, the details of moisture transport toward the Sahel are still unclear, or perhaps there is no single determining influence.

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Section: Global Sst Trend Shiftmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Global Sst Trend Shiftmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Synchrony of trend shifts in Sahel boreal summer rainfall and global oceanic evaporation, 1950–2012

Diawara

Tachibana

Oshima

et al. 2016

Hydrol. Earth Syst. Sci.

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Climate anomalies affect annual survival rates of swifts wintering in sub‐Saharan Africa

Boano

Pellegrino

Ferri

et al. 2020

Ecology and Evolution

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Several species of migratory swifts breed in the Western Palearctic, but they differ in reproductive traits and nonbreeding areas explored in Africa. We examined survival and recapture probabilities of two species of swifts by capture–mark–recapture data collected in northern Italy (Pallid Swift Apus pallidus in Carmagnola, Turin, and Common Swift Apus apus in Guiglia, Modena) in the breeding season (May–July). Apparent survival rates were relatively high (>71%), comparable to other studies of European swifts, but showed marked annual variations. We used geolocators to establish the exact wintering areas of birds breeding in our study colonies. Common Swifts explored the Sahel zone during migration and spent the winter in SE Africa, while the Pallid Swifts remained in the Sahel zone for a longer time, shifting locations southeast down to Cameroun and Nigeria later in winter. These movements followed the seasonal rains from north to south (October to December). In both species, we found large yearly differences in survival probabilities related to different climatic indices. In the Pallid Swift, wintering in Western Africa, the Sahel rainfall index best explained survival, with driest seasons associated with reduced survival. In the Common Swift, wintering in SE Africa, the El Niño–Southern Oscillation (ENSO) cycle performed significantly better than Sahel rainfall or North Atlantic Oscillation (NAO). Extreme events and precipitation anomalies in Eastern Africa during La Niña events resulted in reduced survival probabilities in Common Swifts. Our study shows that the two species of swifts have similar average annual survival, but their survival varies between years and is strongly affected by different climatic drivers associated with their respective wintering areas. This finding could suggest important ecological diversification that should be taken into account when comparing survival and area use of similar species that migrate between temperate breeding areas and tropical wintering areas.

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Moreno¹

2018

Interdecadal Changes in Ocean Teleconnections With the Sahel

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The recent trend of increasing precipitation in Sahel and the associated inter‐hemispheric dipole of global SST

Cited by 19 publications

References 12 publications

Synchrony of trend shifts in Sahel boreal summer rainfall and global oceanic evaporation, 1950–2012

Synchrony of trend shifts in Sahel boreal summer rainfall and global oceanic evaporation, 1950–2012

Climate anomalies affect annual survival rates of swifts wintering in sub‐Saharan Africa

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