Energy balance closure and footprint analysis using Eddy Covariance measurements in Eastern Burkina Faso, West Africa

F. Bagayoko, S. Yonkeu, N. C. van de Giesen
2006 Hydrology and Earth System Sciences Discussions  
Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU Abstract The quality and the representativeness of the first long-term Eddy Covariance measurements in the savanna zone of West Africa were investigated using the energy balance closure and the footprint analysis. The quality and representativeness of the first long-term Eddy Covariance measurements over the West African savanna were 5 investigated using the energy
more » ... ed using the energy balance closure and the footprint analysis. The analysis covered four contrasting periods such as the complete dry season (The results show that the overall energy balance closure can be considered as sat-10 isfactory over the whole dataset. The regression fit between (Rn−G) and (H+λE ) was significant (P <0.05) with a coefficient of determination (r 2 ) of 0.80 and a slope of 0.88, while the intercept was 25 W/m 2 . The energy balance closure was affected by rain during the rainy season (r 2 =0.69), and by sampling problems during the transition periods (R 2 were 0.80 and 0.86, respectively). 15 The footprint analysis shows that the fetch ranged between 20 m (daytime) and 800 m (nighttime). This range showed that the fetch was adequate and fluxes sampled were representative, especially during the rainy season when the vegetal cover was dominated by crops and grasses with scale length of a few meters. During the dry season when the surface is free from crops and grasses, the measurements were also 20 representative as about 60% of the trees around the station were contributing to the measured fluxes. However, during the transition periods some sampling problems appeared, less than 30% of the trees were contributing to the measured fluxes. The relevance of the dominant wind direction in the representativeness of the measurements was also discussed. 25 2790 HESSD 3Abstract HESSD Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU Africa, because sheanut trees dominate the vegetation cover and sorghum is common crop grown widely. The study covers four contrasting periods such as the complete dry season (From Abstract 3Abstract 3Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU where T is temperature [C] in the soil at depth z s [m] and time t [s], α T is the thermal diffusivity [m 2 s −1 ] equal to the ratio of the thermal conductivity over the volumetric heat capacity (C) [J K −1 m −3 ]. When the time and depth increment (∆t) and (∆z s ) are sufficiently small, the solution of Eq. (12) for T t+∆t,z s is expressed as follows (Anlauf et al., 1987): 3Abstract 3Abstract 3Abstract 3Abstract 3
doi:10.5194/hessd-3-2789-2006 fatcat:5snldydzqbhahazxe7nkxuahki