Dynamics of water vapor and energy exchanges above two contrasting Sudanian climate ecosystems in Northern Benin (West Africa)

Abstract

Natural ecosystems in sub‐Saharan Africa are experiencing intense changes that will probably modify land surface feedbacks and consequently the regional climate. In this study, we have analyzed water vapor (QLE) and sensible heat (QH) fluxes over a woodland (Bellefoungou, BE) and a cultivated area (Nalohou, NA) in the Sudanian climate of Northern Benin, using 2 years (from July 2008 to June 2010) of eddy covariance measurements. The evaporative fraction (EF) response to environmental and surface variables was investigated at seasonal scale. Soil moisture was found to be the main environmental factor controlling energy partitioning. During the wet seasons, EF was rather stable with an average of 0.75 ± 0.07 over the woodland and 0.70 ± 0.025 over the cultivated area. This means that 70–75% of the available energy was changed into actual evapotranspiration during the investigated wet seasons depending on the vegetation type. The cumulative annual actual evapotranspiration (AET) varied between 730 ± 50 mm yr−1 at the NA site and 1040 ± 70 mm yr−1 at the BE site. With similar weather conditions at the two sites, the BE site showed 30% higher AET values than the NA site. The sensible heat flux QH at the cultivated site was always higher than that of the woodland site, but observed differences were much less than those of QLE. In a land surface conversion context, these differences are expected to impact both atmospheric dynamics and the hydrological cycle.

Biophysical controls of water vapour and energy fluxes: Towards the development of biome scale predictive models of evapotranspiration in the Albany Thicket, South Africa

“…The observed Ω was lower than those reported by Mamadou et al (2016) who observed values ranging from 0.05-0.45 during the dry and wet season, respectively, in northern Benin. The observed Ω was lower than those reported by Mamadou et al (2016) who observed values ranging from 0.05-0.45 during the dry and wet season, respectively, in northern Benin.…”

“…The low Ω observed suggests that ET was largely controlled by VPD and G s , and the canopy was strongly coupled with the boundary layer. The observed Ω was lower than those reported by Mamadou et al (2016) who observed values ranging from 0.05-0.45 during the dry and wet season, respectively, in northern Benin.…”

Evaporation from cultivated and semi-wild Sudanian Savanna in west Africa

“…The sensible and latent energy fluxes from the fallow were lower than those of the forest in 2010, whereas when short season millet was growing, they were more similar. By comparing the changes in soil moisture along the diurnal cycle, we see that even in the dry season there is some variation, particularly at shallow depths; thus, in contrast to other authors, we cannot attribute the early peak purely to stomata behavior during the dry season (Mamadou et al, 2016). In contrast, during the rainy season, it declined, following the cycle of available radiation.…”

“…These values are in general higher than previously found in similar environments during the rainy season (Bagayoko et al, 2007;Brümmer et al, 2008;Guyot et al, 2012;Mamadou et al, 2016). In contrast, our site has a lower dry season evaporative fraction than nearby sites, which suggests that moisture cycling during the wet season is more complete and that there is less storage into the dry season.…”

“…These land covers are representative of the surrounding region and capture the range from more to less anthropogenic land uses. The multi-use comparison over multiple seasonal cycles puts this study among the few recent, long-term studies in this region (Bagayoko et al, 2007;Brümmer et al, 2008;Ezzahar et al, 2009;Guichard et al, 2009;Guyot et al, 2009, Lohou et al, 2010Mamadou et al, 2014Mamadou et al, , 2016Mauder et al, 2006;Ramier et al, 2009;Timouk et al, 2009;Velluet et al, 2014). We calculate the evaporative fraction over the study period and compare it with land cover and atmospheric controls, in order to provide estimation based on the physical basis of fluxes.…”