Validity of the Landsat surface reflectance archive for aquatic science: Implications for cloud‐based analysis

Abstract

Originally developed for terrestrial science and applications, the US Geological Survey Landsat surface reflectance (SR) archive spanning ~ 40 yr of observations has been increasingly utilized in large‐scale water‐quality studies. These products, however, have not been rigorously validated using in situ measured reflectance. This letter quantifies and demonstrates the quality of the SR products by harnessing a sizeable global dataset (N = 1100). We found that the Landsat 8/9 SR in the green and red bands marginally meet the targeted accuracy requirements (30%), whereas the uncertainties in the blue and coastal‐aerosol bands ranged from 48% to 110%. We further observed > +25% biases in the visible bands of Landsat 5/7 SR, which can introduce an apparent downward trend when applied in time‐series analyses combined with Landsat 8/9. Users must exercise caution when using this archive for trend analyses, and progress in atmospheric correction is required to foster advanced applications of the Landsat archive for aquatic science.

Long‐Term Trends in Productivity Across Intermountain West Lakes Provide No Evidence of Widespread Eutrophication

“…Given the differences between the spectral response of Landsat sensors, we used this comprehensive set of surface reflectance observations to standardize surface reflectance across sensors. Recent studies have found that these differences, if not corrected for, can distort time‐series analyses and produce misleading downward trends (Maciel et al., 2023). This apparent bias has the potential to have widespread effects on the results of trend analyses of water quality data, where observed improvements in water quality trends (downward trends) is a product of these sensor differences.…”