Land Cover Signature on the Convective Rainfall Mechanism over a Sudanian Savannah Basin, Tambarga, Burkina Faso.

Friday, 19 December 2014
Theophile Mande1,2, Natalie C Ceperley1, Gabriel George Katul3, Hamma Yacouba2, Andrea Rinaldo1 and Marc B Parlange1,4, (1)EPFL Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland, (2)International Institute for Water and Environmental Engineering, Ouagadougou, Burkina Faso, (3)Duke University, Durham, NC, United States, (4)University of British Columbia, Civil Engineering, Vancouver, BC, Canada
For water limited areas such as southeastern Burkina Faso where the main activity is rainfed agriculture, it is crucial to understand the rainfall mechanism and its main drivers. The triggering convective mechanisms are important and contribute to more than 30% of the total rainfall. Several studies were devoted to the convective rainfall characterization. However, the rainfall partitioning between convective and non-convective events and the effects of land cover signature on the rainfall type at small scales remain relatively unexplored topics.

The following study aims to investigate the triggering mechanisms of rainfall and their interaction with land cover. For this purpose a simple realistic model combining the mixed layer growth (ML) and lifting condensation level (LCL) was implemented for convective rainfall tracking. Convective events occur when the LCL and ML curves intersect at the time corresponding to the rain event start. Sensible heat flux, air temperature and humidity measurements used for this analysis were collected over three years with twelve advanced weather monitoring Sensorscope stations and two eddy flux towers distributed over two different landscapes, an agricultural field and an savanna forest

The land cover signature evidence is highlighted by the similarity of the pdf of the rainfall over the forested region and agricultural fields with a slope -1.5. While a 10 to 30% difference in total yearly precipitation is observed between the agriculture zone and the forest region. Therefore, in addition to the soil moisture, higher temperature (Clausius-Clapeyron) and CO2 effect on rainfall mechanisms, the local land cover signature should be added for better rainfall modeling.