Impact of dynamical regionalization on precipitation biases and teleconnections over West Africa

Gómara, Íñigo; Mohíno, Elsa; Losada, Teresa; Domínguez, Marta; Suárez-Moreno, Roberto; Rodríguez‐Fonseca, Belén

doi:10.1007/s00382-017-3886-4

Cited by 14 publications

(18 citation statements)

References 93 publications

(128 reference statements)

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“…ERA-Interim is provided at 0.758 3 0.758 horizontal resolution with 60 vertical atmospheric levels, from the surface up to 0.1 hPa (Dee et al 2011). The dynamical fields analyzed to compute JJAS seasonal anomalies are (i) specific humidity at 850 hPa; (ii) moisture flux at 850 hPa; and (iii) vertical instability, which is the difference of wind divergence between the 200-and 850-hPa pressure levels (hereafter DIV200/850; Gómara et al 2018). Positive DIV200/850 values thus indicate vertical destabilization and upward motion of air (the reverse is true for negative values).…”

Section: Methodsmentioning

confidence: 99%

“…Positive DIV200/850 values thus indicate vertical destabilization and upward motion of air (the reverse is true for negative values). The sea level pressure (SLP) is also used (instead of the DIV200/850 parameter) for the MSI, as the influence of the Mediterranean Sea in Sahelian rainfall has been found to take place through anomalous moisture advection at surface levels, mediated by the SLP gradient between the Gulf of Guinea and the Sahara (Rowell 2013;Fontaine et al 2010;Gómara et al 2018).…”

Section: Methodsmentioning

confidence: 99%

“…Among processes controlling Sahel rainfall variability, oceanic forcing has been found to be the dominant driver (Giannini et al 2003;Rowell 2013;Rodríguez-Fonseca et al 2011Gómara et al 2018). Many works have shown that seasonal rainfall variability over the Sahel is related to sea surface temperature (SST) anomalies over the tropical Atlantic, Pacific, and the Mediterranean Sea (Rodríguez-Fonseca et al 2015, and references therein).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Oceanic Forcing on Interannual Variability of Sahel Heavy and Moderate Daily Rainfall

Diakhaté

Rodríguez‐Fonseca

Gómara

et al. 2019

Journal of Hydrometeorology

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This article analyzes SST remote forcing on the interannual variability of Sahel summer (June–September) moderate (below 75th percentile) and heavy (above 75th percentile) daily precipitation events during the period 1981–2016. Evidence is given that interannual variability of these events is markedly different. The occurrence of moderate daily rainfall events appears to be enhanced by positive SST anomalies over the tropical North Atlantic and Mediterranean, which act to increase low-level moisture advection toward the Sahel from the equatorial and north tropical Atlantic (the opposite holds for negative SSTs anomalies). In contrast, heavy and extreme daily rainfall events seem to be linked to El Niño–Southern Oscillation (ENSO) and Mediterranean variability. Under La Niña conditions and a warmer Mediterranean, vertical atmospheric instability is increased over the Sahel and low-level moisture supply from the equatorial Atlantic is enhanced over the area (the reverse is found for opposite-sign SST anomalies). Further evidence suggests that interannual variability of Sahel rainfall is mainly dominated by the extreme events. These results have implications for seasonal forecasting of Sahel moderate and heavy precipitation events based on SST predictors, as significant predictability is found from 1 to 4 months in advance.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oceanic Forcing on Interannual Variability of Sahel Heavy and Moderate Daily Rainfall

Diakhaté

Rodríguez‐Fonseca

Gómara

et al. 2019

Journal of Hydrometeorology

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“…The difference of the wind divergence between 200 hPa and 850 hPa levels (DIV200/850) is used to evaluate the direction and intensity of the vertical air motion (Gómara et al, 2017;Diakhaté et al, 2019). Positive values of this difference (upper level minus low level) means that there is a low level convergence of the wind, an ascent and a divergence at high level.…”

Section: Methodsmentioning

confidence: 99%

Weakened impact of the Atlantic Niño on the future equatorial Atlantic and Guinean Coast rainfall

Worou

Goosse

Fichefet

et al. 2021

Preprint

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Abstract. The Guinea Coast is the southern part of the West African continent. Its summer rainfall variability mostly occurs on interannual timescales and is highly influenced by the sea surface temperature (SST) variability in the eastern equatorial Atlantic, which is known as the Atlantic Niño (ATL3). Using historical simulations from 31 General Circulation Models (GCMs) participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), we first show that these models are able to simulate reasonably well the rainfall annual cycle in the Guinea Coast, with, however, a wet bias during boreal summer. This bias is associated with too high mean summer SSTs in the eastern equatorial and south Atlantic regions. Next, we analyze the near-term, mid-term and long-term changes of the Atlantic Niño mode relative to the present-day situation, in a climate with a high anthropogenic emission of greenhouse gases. We find a gradual decrease of the equatorial Atlantic SST anomalies associated with the Atlantic Niño in the three periods of the future. This result reflects a possible reduction of the Atlantic Niño variability in the future due to a weakening of the Bjerkness feedback over the equatorial Atlantic. In a warmer climate, an oceanic extension of the Saharan Heat Low over the North Atlantic and an anomalous higher sea level pressure in the western equatorial Atlantic relative to the eastern equatorial Atlantic weaken the climatological trade winds over the equatorial Atlantic. As a result, the eastern equatorial Atlantic thermocline is deeper and responds less to Atlantic Niño events. Among the models that simulate a realistic rainfall pattern associated with ATL3 in the present-day climate, there are 15 GCMs which project a decrease of the Guinean Coast rainfall response related to ATL3, and 9 GCMs which show no substantial change in the patterns associated with ATL3. In these 15 models, the zonal wind response to the ATL3 over the equatorial Atlantic is strongly attenuated in the future climate. Similar results are found when the analysis is focused on the rainfall response to ATL3 over the equatorial Atlantic. There is a higher confidence in the reduction of the rainfall associated with ATL3 over the Atlantic Ocean than over the Guinea Coast. We also found a decrease of the convection associated with ATL3 in the majority of the models.

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“…Even if RCMs have been proved to be a useful tool to describe climatic features in the tropics (Nikulin et al, 2012;Gómara et al, 2018) and extratropics (Jacob et al, 2014;Casanueva et al, 2015), they still present biases in temperature and precipitation over Europe (Casanueva et al, 2016;Dosio, 2016), overestimating future temperature projections for instance (Boberg and Christensen, 2012). Several techniques have been developed so far to minimise and handle model biases, as future projections of threshold-based indices may not be reliable when models' outputs are used without prior bias adjustment.…”

mentioning

confidence: 99%

Chilling accumulation in temperate fruit trees in Spain under climate change

Rodríguez¹,

Pérez-López²,

Sánchez³

et al. 2019

Preprint

Self Cite

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Abstract. Temperate fruit trees account for almost half of the worldwide fruit production, with Spain one of the largest world producers. Growing trees are quite vulnerable to cold temperatures. To minimise the effect of these cold temperatures, they stop their growth over the coldest months of the year, a state called dormancy. In particular, endodormancy, i.e. a dormancy related to the plant's inner physiological factors, requires accumulating cool temperatures to finish dormancy (be broken). The accumulation of cool temperatures according to specific rules is called chilling accumulation, and the chilling accumulation required to break dormancy is different for each tree crop and variety. There are several methods to calculate the chilling accumulation, all of them based on temperature only. Under global warming, it is expected that the fulfilment of the chilling requirements to break dormancy in temperate fruit trees could be compromised. In this study, the impact of climate change on the chilling accumulation over Peninsular Spain and the Balearic Islands was assessed. For this, bias-adjusted results of 10 Regional Climate Models (RCMs) under Representative Concentration Pathways (RCPs) RCP4.5 and RCP8.5 were used as inputs of four different methods for calculating chilling accumulation, and the results were compared for the near and far future under both RCPs. These results project a generalised reduction in chilling accumulation regardless of the RCP, future period or chilling calculation method used, with higher reductions for the far future and the RCP8.5 scenario. The projected winter chill decrease may threaten the viability of some tree crops and varieties in some areas, but also shows scope for varieties with lower chilling requirements. The results are relevant for planning future tree plantations under climate change, supporting adaptation of spatial distribution of tree crops and varieties in Spain.

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Impact of dynamical regionalization on precipitation biases and teleconnections over West Africa

Cited by 14 publications

References 93 publications

Oceanic Forcing on Interannual Variability of Sahel Heavy and Moderate Daily Rainfall

Oceanic Forcing on Interannual Variability of Sahel Heavy and Moderate Daily Rainfall

Weakened impact of the Atlantic Niño on the future equatorial Atlantic and Guinean Coast rainfall

Chilling accumulation in temperate fruit trees in Spain under climate change

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