Contrasted land‐surface processes along the West African rainfall gradient

Séguis, Luc; Boulain, N.; Cappelaere, Bernard; Cohard, Jean‐Martial; Favreau, Guillaume; Galle, Sylvie; Guyot, Adrien; Hiernaux, Pierre; Mougin, E.; Peugeot, Christophe; Ramier, David; Seghieri, Josiane; Timouk, Franck; Demarez, Valérie; Demarty, Jérôme; Descroix, Luc; Descloîtres, Marc; Grippa, Manuela; Guichard, Françoise; Kamagaté, Bamory; Kergoat, Laurent; Lebel, Thierry; Dantec, Valérie Le; Lay, Matthieu Le; Massuel, Sylvain; Trichon, Valérie

doi:10.1002/asl.327

Cited by 25 publications

(18 citation statements)

References 23 publications

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“…Gardelle et al (2010) established that the surface of ponds in the Gourma dramatically increased during the multidecadal drought, despite lower rainfall amounts. This paradox, which is in line with the increased runoff in the Sahel Séguis et al, 2011), differs in the sense that it does not result from a change in cultivated area, as often advocated for runoff changes in the cultivated Sahel. Such an increase has a direct impact in water resource assessment and perception by local societies.…”

Section: Looking Backwardmentioning

confidence: 84%

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Remote sensing of the land surface during the African Monsoon Multidisciplinary Analysis (AMMA)

Kergoat

Grippa

Baille

et al. 2011

Atmospheric Science Letters

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Section: Looking Backwardmentioning

confidence: 84%

“…Secondly, AMMA also moved toward more integration of the EO activities into thematic workpackages (e.g. Séguis et al, 2011;Taylor et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Remote sensing of the land surface during the African Monsoon Multidisciplinary Analysis (AMMA)

Kergoat

Grippa

Baille

et al. 2011

Atmospheric Science Letters

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“…The rainfall gauge network data in Benin showed 1289.09 mm during the experiment period, while it was 358.52 mm in Niger [23]. The Analyses Multidisciplinaires de la Mousson Africaine (AMMA) field campaign for this region was established in Benin and Niger for the purpose of calibration and validation of satellite data, as previously introduced by [25,26]. Detailed super-site locations for Benin and Niger are available at http://www.amma-catch.org/.…”

Section: Methodsmentioning

confidence: 99%

A Novel Bias Correction Method for Soil Moisture and Ocean Salinity (SMOS) Soil Moisture: Retrieval Ensembles

Lee

2015

Remote Sensing

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Bias correction is a very important pre-processing step in satellite data assimilation analysis, as data assimilation itself cannot circumvent satellite biases. We introduce a retrieval algorithm-specific and spatially heterogeneous Instantaneous Field of View (IFOV) bias correction method for Soil Moisture and Ocean Salinity (SMOS) soil moisture. To the best of our knowledge, this is the first paper to present the probabilistic presentation of SMOS soil moisture using retrieval ensembles. We illustrate that retrieval ensembles effectively mitigated the overestimation problem of SMOS soil moisture arising from brightness temperature errors over West Africa in a computationally efficient way (ensemble size: 12, no time-integration). In contrast, the existing method of Cumulative Distribution Function (CDF) matching considerably increased the SMOS biases, due to the limitations of relying on the imperfect reference data. From the validation at two semi-arid sites, Benin (moderately wet and vegetated area) and Niger (dry and sandy bare soils), it was shown that the SMOS errors arising from rain and vegetation attenuation were appropriately corrected by ensemble approaches. In Benin, the Root Mean Square Errors (RMSEs) decreased from 0.1248 m 3 /m 3 for CDF matching to 0.0678 m 3 /m 3 for the proposed ensemble approach. In Niger, the RMSEs decreased from 0.14 m 3 /m 3 for CDF matching to 0.045 m 3 /m 3 for the ensemble approach.

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“…1 Location of the two studied eddy-covariance sites and their land use distributions on a 1-km 2 area around the tower a in West Africa, b forest (Bellefoungou), and c savannah (Nalohou) Fig. 2 View of both ecosystems during the dry (below) and wet seasons (above): savannah (a, b) and forest (c, d) during the wet season, the water table closes always from the ground surface (2-3 m), but does not exceed a depth of 6-10 m during the dry season (Séguis et al 2011). The savannah site vegetation is relatively heterogeneous.…”

Section: Two Sites' Descriptionmentioning

confidence: 99%

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

Ago

Agbossou

Cohard

et al. 2016

Annals of Forest Science

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& Key message CO 2 fluxes were measured during 18 months in a forest and a savannah in northern Benin. Higher values of carbon fluxes were found during the wet season at each site. A strong dependency of carbon fluxes on water relations was found in two contrasting sites. The forest sequestered 640 ± 50 and the savannah 190 ± 40 g C m −2 year −1 . & Context In West Africa, the main mechanisms or factors governing the dynamics of ecosystems, especially the dynamics of the carbon fluxes and productivity, still remain less known. This study reports the carbon fluxes over two contrasting ecosystems, notably a protected forest (lat 9.79°N, long 1.72°E, alt 414 m) and a cultivated savannah (lat 9.74°N, long 1.60°E, alt 449 m) in northern Benin. The two sites were among those equipped by the AMMA-CATCH observatory and Ouémé 2025 project. & Aims Flux data were analyzed at the daily and seasonal scales in order to understand their controlling variables. We discussed the patterns of CO 2 fluxes and the characteristics of the two ecosystems. The study also focused on the different water usage strategies developed by the two ecosystems since the alternation between dry and wet seasons highly influenced the seasonal dynamics. Finally, the annual carbon sequestration was estimated together with its uncertainty. & Methods The carbon fluxes were measured during 18 months (July 2008-December 2009) by an eddy-covariance system over two contrasting sites in northern Benin. Fluxes data were computed following the standard procedure. The responses of CO 2 fluxes to the principal climatic and edaphic factors, and the canopy conductance were studied. & Results A clear CO 2 fluxes response to main environmental factors was observed, however with difference according to the seasons and vegetation types. The ecosystem respiration showed the highest values during the wet season and a progressive decrease from wet to dry periods. Also, the carbon uptake values were high during the wet period, but Handling Editor: Erwin DreyerContribution of the co-authors Expédit Evariste Ago conducted mainly the data analysis and prepared the manuscript with contributions from all co-authors. The field work with the eddy-covariance technique was carried out by Jean-Martial Cohard and Sylvie Galle who processed the raw data of fluxes. Marc Aubinet and Euloge Kossi Agbossou assisted in the data analyses. All authors read and approved the final manuscript which was submitted. low during the dry period. However, the CO 2 fluxes for the protected forest were always higher than that for the cultivated savannah within each defined period. This was due to the seasonal changes not only in phenology and physiology but also to the acclimation to environmental conditions, especially to the soil water availability. The water use efficiency was influenced by VPD during the day conditions for two ecosystems. However, the VPD response curve of water usage was relatively constant for the protected forest during the transitional and wet seasons. In contrary, for t...

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Contrasted land‐surface processes along the West African rainfall gradient

Cited by 25 publications

References 23 publications

Remote sensing of the land surface during the African Monsoon Multidisciplinary Analysis (AMMA)

Remote sensing of the land surface during the African Monsoon Multidisciplinary Analysis (AMMA)

A Novel Bias Correction Method for Soil Moisture and Ocean Salinity (SMOS) Soil Moisture: Retrieval Ensembles

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

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