Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

Sales, Fernando De; Xue, Yongkang; Okin, Gregory S.

doi:10.1007/s00382-015-2522-4

Cited by 27 publications

(29 citation statements)

References 44 publications

(58 reference statements)

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“…Alternatively, feedbacks associated with increased albedo have been implicated as a cause of reduced precipitation at a variety of scales [ Charney et al ., ; Meng et al ., ]. In this scenario the exposure of dry soils after vegetation is removed by fire leads to increased albedo, decreased net radiation, and total heat flux into the atmosphere and a less energetic planetary boundary layer that inhibits convective processes, a finding supported by modeling [ de Sales et al ., ]. Evidence of long‐term brightening has been found over semiarid burn scars but is dependent on the timing of fire and underlying soils [ Veraverbeke et al ., ; Gatebe et al ., ].…”

Section: Resultsmentioning

confidence: 99%

“…Evidence of long‐term brightening has been found over semiarid burn scars but is dependent on the timing of fire and underlying soils [ Veraverbeke et al ., ; Gatebe et al ., ]. Overall, studies reporting modeled rainfall reductions after fire suggest that the net effect of fire is a drier, more stable planetary boundary layer with stronger atmospheric subsidence and reduced moisture flux convergence [ Notaro et al ., ; de Sales et al ., ]. Indirect mechanisms may also play a role in maintaining or amplifying early wet season rainfall deficits.…”

Section: Resultsmentioning

confidence: 99%

“…However, another study over the same region but using a different modeling approach reports a significant 0.5 mm d −1 decrease in premonsoonal precipitation [ Notaro et al ., ]. Similarly, a modeling experiment focusing on West Africa showed that fire strengthens atmospheric subsidence by increasing albedo and reducing net radiation, leading to a 3% reduction in wet season precipitation [ de Sales et al ., ]. A case study [ Hernandez et al ., ] of local changes in precipitation after extensive wildfires in Portugal is less conclusive, showing either enhancement or suppression depending on the representation of rainfall processes in the model.…”

Section: Introductionmentioning

confidence: 99%

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Suppression of rainfall by fires in African drylands

Saha

Scanlon

D’Odorico

2016

Geophysical Research Letters

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Fire is a widespread agent of disturbance in African drylands, but the impact of fire on local precipitation remains poorly understood and large‐scale observational evidence has been lacking. Here we link fire to a reduction in precipitation across African drylands. Using 15 years of satellite observations over continental sub‐Saharan Africa, we find that more extensive and later dry season fires lead to wet season rainfall deficits of up to 30 mm (~10%). The effect is stronger in the Southern Hemisphere, a signal we attribute to the later timing of fires in the dry season. Given the coupling between rainfall, fuel loads, and fire in African drylands, a negative interannual feedback may arise between fire and precipitation, whereby fires suppress precipitation, thereby reducing fuel load and fire in the subsequent season. The reduced fuel load would, in turn, increase precipitation, completing the feedback loop. This feedback may contribute to a pervasive negative autocorrelation observed in Southern Hemisphere annual rainfall.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Suppression of rainfall by fires in African drylands

Saha

Scanlon

D’Odorico

2016

Geophysical Research Letters

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“…The WAMME II also includes regional climate models (Table 2). Results from RCM in relation to monsoon response to LULCC and biomass burning are presented in separate papers (Hagos et al 2014;De Sales et al 2015;Wang et al 2015). The WAMME II control simulation (referred to as Case CTL) uses January 1, 2006, as the initial condition and time-varying climatological SSTs as boundary conditions.…”

Section: Wamme Models and Wamme II Experimental Designmentioning

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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“…The main themes of this A number of WAMME II studies were carried out using RCMs as well. De Sales et al (2016) assess the impact of changes in vegetation condition and surface albedo over biomass-burned areas on the surface energy balance and WAM monthly evolution as simulated by a RCM. Wang et al (2016) investigate LULCC impact on the WAM using a RCM with different lateral boundary conditions (LBC), one from reanalysis data for both control and LULCC simulations and another obtained from the corresponding control and LULCC GCM simulations, and compare the LBCs' influence on the simulated LULCC impact.…”

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confidence: 99%

Variability and predictability of West African monsoon on seasonal and decadal scales

2016

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special issue are: (1) intercomparison and evaluation of skills of GCMs and RCMs in simulating seasonal and decadal variability of WAM rainfall and relevant processes, and its association with SST, LULCC, and aerosol processes, as well as identification of major challenges, deficiencies, and uncertainties that remain in modeling WAM variability; (2) representations of major WAM characteristics and possible underlying physical and dynamic mechanisms; (3) application of observational and reanalyses data as a pathway for model physics evaluation and improvement, and in understanding the WAM variability; and (4) evaluation of RCM downscaling ability in terms of WAM decadal variability. The papers in the special issue are mainly based on research conducted in conjunction with the second phase of the international West African Monsoon Modeling and Evaluation (WAMME II) project and the African Multidisciplinary Monsoon Analysis (AMMA) project.Most papers in this issue are from the WAMME II project focusing on the interactions between the WAM and external forcings. In the WAMME II experiment, realistic but idealized forcings (setting to maximum forcing amplitude) are imposed to examine WAM responses in the WAMME II models. Among them, Xue et al. (2016) investigate relative effects of the global and several major individual ocean basins on the WAM decadal variability and compare the SST's role and the LULCC effect in initiating and modulating the decadal WAM variability and the 1980s Sahel drought. Boone et al. (2016) use recently available LULCC data to evaluate the sensitivity of WAM seasonal variability to land surface processes and physical mechanisms involved. In addition to multi-model experiments, some of the individual models' results are also presented. Using the aerosol data from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, Gu et al. (2016) compare aerosol effects over the WAM region and the Asian monsoon regions.Recent observational evidence supports the notion that there are strong decadal climate variabilities in the Sahel and surrounding areas from the 1950s to the 2000s, not only in precipitation, but also in sea surface temperature (SST), vegetation cover, land use and land cover change (LULCC), and aerosol loading and spatial distributions Boone et al. 2016;Gu et al. 2016). In the 2010 Climate Dynamics Special Issue "West African Monsoon and its Modeling," the skills of general circulation models (GCMs) and regional climate models (RCMs) in properly simulating the West African monsoon (WAM) were extensively evaluated, and possible causes that contribute to model deficiencies were investigated. While these studies provided basic understanding of the seasonal variations of WAM climatology, understanding of the complex interactions of WAM variability associated with SST, land surface, and aerosol forcings at different scales, particularly with respect to seasonal to decadal scale forcing, is still lacking.This special issue "Decadal variability of the West African monsoon, external ...

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Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

Cited by 27 publications

References 44 publications

Suppression of rainfall by fires in African drylands

Suppression of rainfall by fires in African drylands

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 monsoon on seasonal and decadal scales

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