Venturini, V, Bisht, G, Islam, S, Jiang, L (2004). Comparison of evaporative fractions estimated from AVHRR and MODIS sensors over South Florida. REMOTE SENSING OF ENVIRONMENT, 93(2-Jan), 77-86.
Remote sensing cannot provide a direct measurement of evapotranspiration (ET) but it can provide a reasonably good estimate of Evaporative Fraction (EF), defined as the ratio of ET and available energy. Recent studies have successfully estimated EF using a contextual interpretation of radiometric surface temperature (TO) and normalized difference vegetation index (NDVI) such as from the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA-14 satellite. To provide a continuous monitoring capability for EF, it is important to explore the utility of such an approach to recently launched sensors with better spectral resolution. Here, we explore the utility of Moderate Resolution Imaging Spectroradiometer (MODIS), onboard EOS Terra satellite, sensors to estimate EF over large areas. We compare and contrast EF estimates from AVHRR and MODIS sensors over South Florida. We also explore the sensitivity of NDVI and T-0 to sensor response functions (SRFs) and atmospheric variables. Our results show that NDVI-T-0 space, when using T-0 from a single channel derived temperature, is affected by the SRFs and overpass times. Despite differences in NDVI and T-0 estimates from AVHRR and MODIS sensors, it appears that they capture similar contextual information of energy partitioning and the EF estimates are comparable. Our results suggest that the proposed EF estimation is relatively insensitive to changes in absolute values of T-0, induced by local atmospheric conditions and sensor viewing angles, and EF is primarily determined by the overall contextual space of NDVI-T-0 diagram. (C) 2004 Elsevier Inc. All rights reserved.