Influence of soil properties on latent and sensible heat transport in the major soil types in Western Senegal

Understanding soil-moisture-atmosphere interactions is essential for a range of applications like accurate weather forecasting and climate modelling. However, current models often overlook critical soil properties, particularly soil hydraulic parameters (SHP), limiting their accuracy. The Sahel region, characterized by intense evaporation-precipitation feedback and recycling of up to 95% of rainfall, provides an ideal setting to study these dynamics. Despite its significance, data on SHP remains scarce for this region. 

In the context of the DakE-project, which operates a high-resolution network of weather stations including soil moisture monitoring in Western Senegal, this study investigates the influence of SHP on heat fluxes across five soil types, covered by the network. SHP were characterized by constructing water retention curves based on on-site observations of soil moisture and soil suction and sampled physical soil properties. A coupled water and heat transport model was developed in HYDRUS-1D, incorporating vegetation effects to explore the influence of SHP, particularly on latent heat flux. Site-specific initial and boundary conditions were applied to construct and calibrate five models against observed soil moisture data. Model outputs from the different study sites were compared to evaluate the role of SHP on heat flux partitioning

Preliminary results, derived from Pearson correlation test, indicate a positive correlation between clay content and latent heat flux, with higher clay content increasing latent heat and the probability of precipitation. The same relationship is observed for saturated hydraulic conductivity, which is strongly influenced by soil texture and structure. These findings, while limited to data from only five study sites and influenced by interconnected nature of soil properties, highlight the potential importance of soil texture and structure as key parameters for precipitation modelling. As we show in this study, the drastic seasonal differences in soil wetness behaviour – from desert-like in dry season to prolonged inundation periods during wet season – makes the choice of model set up not trivial and can make model calibration challenging. Our findings underscore the need to better understand the soil water-atmosphere interactions in the Sahel region.

Besides the small spatial scale considered in this study, our study emphasizes the importance of SHP for process understanding not only in soil hydrology but also in atmospheric sciences. Interdisciplinary approach is imperative to incorporate soil texture and structure into current climate models, improving their representation of soil-atmosphere feedbacks in the Sahel and beyond.