Improving the AVHRR’s BRDF correction using MODIS

Abstract

The Long Term Data Record (LTDR) has the goal of developing a quality and consistent AVHRR surface reflectance product using the MODIS instrument as a reference. When a surface reflectance time series is acquired from satellites with variable observation geometry, the directional variation generates an apparent noise which can be corrected by modeling the bidirectional reflectance distribution function (BRDF). The well-established MODIS-based VJB method estimates a target’s BRDF shape and corrects for directional effects, maintaining the high temporal resolution of the measurement, but its viability and optimization for AVHRR data hasn’t been fully explored. In this study we explore different approaches to find the most robust way of applying the VJB correction in AVHRR data, considering that high noise in the AVHRR’s red band (B1) makes the VJB method unstable. Our results show that 1-the VJB method can be modified to improve the stability of the correction parameters in AVHRR by ~5% and that 2- the time series noise using MODIS correction parameters is comparable to that using AVHRR derived parameters.