Combining the triangle method with thermal inertia to estimate regional evapotranspiration — Applied to MSG-SEVIRI data in the Senegal River basin

• DOI: 10.1016/j.rse.2007.08.013
• Publication Date: 2007-12-04T15:13:27Z
• Authors: Simon Stisen; Inge Sandholt; Anette Nørgaard; Rasmus Fensholt; Karsten Høgh Jensen
• Keywords: Evapotranspiration; Triangle method; NDVI; 0207 environmental engineering; 02 engineering and technology; Remote sensing; 15. Life on land; 6. Clean water; MSG SEVIRI; Surface temperature; overflade temperatur; 13. Climate action; Faculty of Science; /dk/atira/pure/core/keywords/TheFacultyOfScience; Evaporative fraction; Thermal inertia

Abstract Spatially distributed estimates of evaporative fraction and actual evapotranspiration are pursued using a simple remote sensing technique based on a remotely sensed vegetation index (NDVI) and diurnal changes in land surface temperature. The technique, known as the triangle method, is improved by utilizing the high temporal resolution of the geostationary MSG-SEVIRI sensor. With 15 min acquisition intervals, the MSG-SEVIRI data allow for a precise estimation of the morning rise in land surface temperature which is a strong proxy for total daytime sensible heat fluxes. Combining the diurnal change in surface temperature, dTs with an interpretation of the triangular shaped dTs − NDVI space allows for a direct estimation of evaporative fraction. The mean daytime energy available for evapotranspiration (Rn − G) is estimated using several remote sensors and limited ancillary data. Finally regional estimates of actual evapotranspiration are made by combining evaporative fraction and available energy estimates. The estimated evaporative fraction (EF) and actual evapotranspiration (ET) for the Senegal River basin have been validated against field observations for the rainy season 2005. The validation results showed low biases and RMSE and R2 of 0.13 [−] and 0.63 for EF and RMSE of 41.45 W m− 2 and R2 of 0.66 for ET.