TY - JOUR

T1 - Leaf pigment retrieval using the PROSAIL model

T2 - Influence of uncertainty in prior canopy-structure information

AU - Sun, Jia

AU - Wang, Lunche

AU - Shi, Shuo

AU - Li, Zhenhai

AU - Yang, Jian

AU - Gong, Wei

AU - Wang, Shaoqiang

AU - Tagesson, Torbern

PY - 2022

Y1 - 2022

N2 - Leaf pigments are critical indicators of plant photosynthesis, stress, and physiological conditions. Inversion of radiative transfer models (RTMs) is a promising method for robustly retrieving leaf biochemical traits from canopy observations, and adding prior information has been effective in alleviating the "ill-posed" problem, a major challenge in model inversion. Canopy structure parameters, such as leaf area index (LAI) and average leaf inclination angle (ALA), can serve as prior information for leaf pigment retrieval. Using canopy spectra simulated from the PROSAIL model, we estimated the effects of uncertainty in LAI and ALA used as prior information for lookup table-based inversions of leaf chlorophyll (C-ab) and carotenoid (C-ar). The retrieval accuracies of the two pigments were increased by use of the priors of LAI (RMSE of C(ab )from 7.67 to 6.32 mu g cm(2) , C-ar from 2.41 to 2.28 mu g cm(2)) and ALA (RMSE of C-ab from 7.67 to 5.72 mu g cm(2) , C-ar from 2.41 to 2.23 mu g cm(2)). However, this improvement deteriorated with an increase of additive and multiplicative uncertainties, and when 40% and 20% noise was added to LAI and ALA respectively, these priors ceased to increase retrieval accuracy. Validation using an experimental winter wheat dataset also showed that compared with C-ar , the estimation accuracy of C-ab increased more or deteriorated less with uncertainty in prior canopy structure. This study demonstrates possible limitations of using prior information in RTM inversions for retrieval of leaf biochemistry, when large uncertainties are present. (C) 2022 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.

AB - Leaf pigments are critical indicators of plant photosynthesis, stress, and physiological conditions. Inversion of radiative transfer models (RTMs) is a promising method for robustly retrieving leaf biochemical traits from canopy observations, and adding prior information has been effective in alleviating the "ill-posed" problem, a major challenge in model inversion. Canopy structure parameters, such as leaf area index (LAI) and average leaf inclination angle (ALA), can serve as prior information for leaf pigment retrieval. Using canopy spectra simulated from the PROSAIL model, we estimated the effects of uncertainty in LAI and ALA used as prior information for lookup table-based inversions of leaf chlorophyll (C-ab) and carotenoid (C-ar). The retrieval accuracies of the two pigments were increased by use of the priors of LAI (RMSE of C(ab )from 7.67 to 6.32 mu g cm(2) , C-ar from 2.41 to 2.28 mu g cm(2)) and ALA (RMSE of C-ab from 7.67 to 5.72 mu g cm(2) , C-ar from 2.41 to 2.23 mu g cm(2)). However, this improvement deteriorated with an increase of additive and multiplicative uncertainties, and when 40% and 20% noise was added to LAI and ALA respectively, these priors ceased to increase retrieval accuracy. Validation using an experimental winter wheat dataset also showed that compared with C-ar , the estimation accuracy of C-ab increased more or deteriorated less with uncertainty in prior canopy structure. This study demonstrates possible limitations of using prior information in RTM inversions for retrieval of leaf biochemistry, when large uncertainties are present. (C) 2022 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.

KW - Leaf pigment

KW - PROSAIL model

KW - Canopy structure

KW - Chlorophyll content

KW - Leaf area index

KW - Leaf angle distribution

KW - RADIATIVE-TRANSFER MODELS

KW - AREA INDEX PRODUCTS

KW - CHLOROPHYLL CONTENT

KW - BIOPHYSICAL VARIABLES

KW - HYPERSPECTRAL INDEXES

KW - ANGLE DISTRIBUTION

KW - DRY-MATTER

KW - INVERSION

KW - REFLECTANCE

KW - LAI

U2 - 10.1016/j.cj.2022.04.003

DO - 10.1016/j.cj.2022.04.003

M3 - Journal article

VL - 10

SP - 1251

EP - 1263

JO - Crop Journal

JF - Crop Journal

SN - 2095-5421

IS - 5

ER -