Detecting Canopy Water Status Using Shortwave Infrared Reflectance Data From Polar Orbiting and Geostationary Platforms

Various canopy water status estimates have been developed from recent advances in Earth Observation (EO) technology. A promising methodology is based on the sensitivity of shortwave infrared (SWIR) reflectance to variations in leaf water content. This study explores the potential of SWIR-based canopy water status detection from geostationary Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) data as compared to polar orbiting environmental satellite (POES)-based moderate resolution imaging spectroradiometer (MODIS) data. The EO-based SWIR water stress index (SIWSI) is evaluated against in situ measured canopy water content indicators at a semi-arid grassland savanna site in Senegal 2008. Daily SIWSI from both MODIS and SEVIRI data show an overall inverse relation to Normalized Difference Vegetation Index (NDVI) throughout the growing season. SIWSI observations from SEVIRI are furthermore sensitive to short-term variations of in situ measured plant water content indicators when aboveground biomass increases from 500 to 900 gm
^-2
(LAI ≈ 1-2). MODIS SIWSI observations in contrast do not covary with in situ measured moisture indicators. Spatio-temporal trend analyses performed on SEVIRI SIWSI during a dry period within the growing season support these findings. These results suggest that the combined advantage of an improved temporal resolution and a fixed viewing angle potentially makes the SEVIRI sensor an interesting complementary data source to POES data for SWIR-based canopy water status and stress monitoring in a semi-arid environment.