A multimodel study of the twentieth‐century simulations of Sahel drought from the 1970s to 1990s

Lau, K.-M.; Shen, Shuanghe; Kim, K.-M.; Wang, H.

doi:10.1029/2005jd006281

Cited by 43 publications

(52 citation statements)

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“…Although a number of atmospheric general circulation models (AGCMs) are able to reproduce the twentieth century drying trend in West Africa and the Sahel dry conditions of the 1970-1980s and subsequent rainfall recovery using the observed SST as boundary conditions, simulated trends and drying are substantially weaker than in the observations (e.g., Giannini et al 2003;Lu and Delworth 2005;Hoerling et al 2006Hoerling et al , 2010Lau et al 2006;Caminade and Terray 2010;Martin and Thorncroft 2014). For instance, the Climate of the twentieth century international project (C20C, Scaife et al 2009) used 14 state-of-theart GCMs with observed SSTs and other relevant data to study climate variations and changes over the last century.…”

Section: Introductionmentioning

confidence: 99%

West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

et al. 2016

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in the Sahel climate system at seasonal to decadal scales. The project's strategy is to apply prescribed observationally based anomaly forcing, i.e., "idealized but realistic" forcing, in simulations by climate models. The goal is to assess these forcings' effects in producing/amplifying seasonal and decadal climate variability in the Sahel between the 1950s and the 1980s, which is selected to characterize the great drought period of the last century. This is the first multi-model experiment specifically designed to simultaneously evaluate such relative contributions. The WAMME II models have consistently demonstrated that SST forcing is a major contributor to the twentieth century Sahel drought. Under the influence of the maximum possible SST forcing, the ensemble mean of WAMME II models can produce up to 60 % of the precipitation difference during the period. The present paper also addresses the role of SSTs Abstract The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings This paper is a contribution to the special issue on West African climate decadal variability and its modeling, consisting of papers from the West African Monsoon Modeling and Evaluation (WAMME) and the African Multidisciplinary Monsoon Analyses (AMMA) projects, and coordinated by Yongkang Xue, Serge Janicot, and William Lau. Provided Funding information has to be tagged. Electronic supplementary materialThe online version of this article (doi:10.1007/s00382-016-3224-2) contains supplementary material, which is available to authorized users. 3in triggering and maintaining the Sahel drought. In this regard, the consensus of WAMME II models is that both Indian and Pacific Ocean SSTs greatly contributed to the drought, with the former producing an anomalous displacement of the Intertropical Convergence Zone before the WAM onset, and the latter mainly contributes to the summer WAM drought. The WAMME II models also show that the impact of LULCC forcing on the Sahel climate system is weaker than that of SST forcing, but still of first order magnitude. According to the results, under LULCC forcing the ensemble mean of WAMME II models can produces about 40 % of the precipitation difference between the 1980s and the 1950s. The role of land surface processes in responding to and amplifying the drought is also identified. The results suggest that catastrophic consequences are likely to occur in the regional Sahel climate when SST anomalies in individual ocean basins and in land conditions combine synergistically to favor drought.Keywords Sahel seasonal and decadal climate variability · Sahel drought, SST and land forcings · GCM

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Section: Introductionmentioning

confidence: 99%

West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

et al. 2016

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“…However, Zhang et al (2013) call into question these results as there are multiple inconsistencies between the previous experiments and key aspects of observed variability within and without the North Atlantic. Hoerling et al (2006) and Lau et al (2006) analyzed historical simulations of CGCMs participating in the CMIP3. Overall, the models failed to simulate the midtwentieth-century Sahel drought and recent recovery (Hoerling et al 2010) with the correct magnitude and timing, suggesting that anthropogenic forcings played little or no role in driving the drought.…”

Section: A Role Of Sst Anomaliesmentioning

confidence: 99%

Variability and Predictability of West African Droughts: A Review on the Role of Sea Surface Temperature Anomalies

et al. 2015

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The Sahel experienced a severe drought during the 1970s and 1980s after wet periods in the 1950s and 1960s. Although rainfall partially recovered since the 1990s, the drought had devastating impacts on society. Most studies agree that this dry period resulted primarily from remote effects of sea surface temperature (SST) anomalies amplified by local land surface-atmosphere interactions. This paper reviews advances made during the last decade to better understand the impact of global SST variability on West African rainfall at interannual to decadal time scales. At interannual time scales, a warming of the equatorial Atlantic and Pacific/Indian Oceans results in rainfall reduction over the Sahel, and positive SST anomalies over the Mediterranean Sea tend to be associated with increased rainfall. At decadal time scales, warming over the tropics leads to drought over the Sahel, whereas warming over the North Atlantic promotes increased rainfall. Prediction systems have evolved from seasonal to decadal forecasting. The agreement among future projections has improved from CMIP3 to CMIP5, with a general tendency for slightly wetter conditions over the central part of the Sahel, drier conditions over the western part, and a delay in the monsoon onset. The role of the Indian Ocean, the stationarity of teleconnections, the determination of the leader ocean basin in driving decadal variability, the anthropogenic role, the reduction of the model rainfall spread, and the improvement of some model components are among the most important remaining questions that continue to be the focus of current international projects.

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“…More research is required to systematically evaluate climate models and to exploit fully the observational data, in order to improve the WAM prediction. Thus, far, there have been very few studies evaluating GCMs' performance in simulating the WAM in multi-model experiments (Lau et al 2006;Cook and Vizy 2006;Hoerling et al 2006;Biasutti et al 2009). The West African Monsoon Modeling and Evaluation project (WAMME), a Global Energy and Water Cycle Experiment (GEWEX)/Coordinated Energy and Water Cycle Observation Project (GEWEX/CEOP) initiative in collaboration with the African Monsoon Multi-disciplinary Analysis project (AMMA, Redelsperger et al 2006), uses GCMs and regional climate models (RCMs) to evaluate the performance of current state-of-the-art climate models in simulating the WAM precipitation, onset, withdrawal, and relevant processes at diurnal, intraseasonal, interannual, and interdecadal scales, and to address issues regarding the role of land-ocean-atmosphere interaction, land-cover and land-use change, vegetation dynamics, and aerosols, particularly dust, on WAM development It also identifies common deficiencies among models in simulating the major WAM features and provides better understanding of the fundamental physical processes involved.…”

Section: Introductionmentioning

confidence: 99%

“…SSIB-1 (Xue et al 1991) None UCLA MRF AGCM (Kanamitsu et al 2002;Xue et al 2004) T62L28 (*2°, 28 vertical levels) Chou (1992), Chou and Suarez (1999), Hou et al (1996) SAS (Pan andWu 1995, Hong andPan 1996) SSIB-1 (Xue et al 1991) None References cited in Table 1 Kanamitsu et al 2002b;Xue et al 2004), the UCLA GCM (Mechoso et al 2000;Xue et al 2009), and the COLA (Center for Ocean-Land-Atmosphere Interactions, Kinter III et al 1997) GCM have similar land surface schemes. More information on the physical components of participating models, including land surface models, can be found in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first model intercomparison experiment

et al. 2010

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This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models' (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitudeheight cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail 123Clim Dyn (2010) 35:3-27 DOI 10.1007 to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/ uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting the evidence revealed in the analysis using ALMIP data. An analysis of variability of CEOF modes suggests that the Sahara mode leads the WAM evolution, and divergence in simulating this mode contributes to discrepancies in the precipitation simulation.

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A multimodel study of the twentieth‐century simulations of Sahel drought from the 1970s to 1990s

Cited by 43 publications

References 22 publications

West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

Variability and Predictability of West African Droughts: A Review on the Role of Sea Surface Temperature Anomalies

Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first model intercomparison experiment

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