Mitigating the directional retrieval error of solar-induced chlorophyll fluorescence in the red band

IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Remote Sensing of Environment Pub Date : 2024-11-11 DOI:10.1016/j.rse.2024.114496
Zhaoying Zhang, Yongguang Zhang
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Abstract

Solar-induced chlorophyll fluorescence (SIF) is a promising tool to estimate gross primary production (GPP), but the retrieval of SIF is commonly noisy and highly sensitive to various interference factors. Particularly, the retrieval of SIF in the red band (RSIF) is more challenging than in the far-red SIF (FRSIF) due to the weaker fluorescence signal and the weaker absorption depth of oxygen at the red band compared with the far-red band. A comprehensive evaluation of all factors will allow a reproducible interpretation of SIF signals and advance the estimation of GPP from SIF. Recent studies have assessed the sensitivity of SIF retrieval to sensor characteristics, retrieval methods, and hardware specifications. However, none of these studies have systematically investigated the directional retrieval error of SIF resulting from the mismatch between irradiance measured above the canopy and the true irradiance reaching the canopy components viewed by a sensor. This study illustrated the effect of mismatched irradiance on the retrieval of RSIF using the commonly used standard 3FLD method based on SCOPE model simulations. The retrieval accuracy was highest in the hotspot direction, but it decreased as the observation direction was away from the hotspot. The relative root mean square error (RRMSE) was generally higher than 20 % in the forward directions. To reduce the retrieval error due to the mismatch effect, we proposed a modified 3FLD method (MFLD) by calculating the true irradiance reaching the canopy in a given direction based on geometric optical theory. The results showed that MFLD clearly improved the retrieval accuracy for RSIF, especially in the forward directions where RRMSE decreased by 10 % in most cases. For example, the RRMSE was reduced from 19.26 % to 5.50 % after mitigating the mismatch between the measured and actual solar irradiance, when the solar zenith angle was 40° and viewing zenith angle was 30° in the forward solar principal plane. Even at the nadir observation, the RRMSE was also reduced from 12.84 % to 5.64 %. In summary, MFLD can effectively mitigate the irradiance mismatch effect on the retrieval of RSIF. These results will improve our interpretation of the relationship between GPP and RSIF at different observation directions.
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减小红波段太阳诱导叶绿素荧光的定向检索误差
太阳诱导叶绿素荧光(SIF)是估算总初级生产量(GPP)的一个很有前途的工具,但 SIF 的检索通常噪声很大,而且对各种干扰因素非常敏感。特别是红光波段(RSIF)的 SIF 提取比远红光波段(FRSIF)更具挑战性,因为红光波段的荧光信号比远红光波段弱,氧气的吸收深度也比远红光波段弱。对所有因素进行综合评估将有助于对 SIF 信号进行可重现的解释,并推进根据 SIF 估算 GPP 的工作。最近的研究评估了 SIF 检索对传感器特性、检索方法和硬件规格的敏感性。然而,这些研究都没有系统地调查冠层上方测得的辐照度与传感器观测到的到达冠层成分的真实辐照度之间的不匹配所导致的 SIF 方向性检索误差。这项研究说明了辐照度不匹配对基于 SCOPE 模型模拟的常用标准 3FLD 方法检索 RSIF 的影响。热点方向的检索精度最高,但随着观测方向远离热点,精度有所下降。前进方向的相对均方根误差(RRMSE)普遍高于 20%。为了减少由于错配效应造成的检索误差,我们提出了一种改进的 3FLD 方法(MFLD),即根据几何光学理论计算在给定方向上到达冠层的真实辐照度。结果表明,MFLD 明显提高了 RSIF 的检索精度,尤其是在前向,RRMSE 在大多数情况下降低了 10%。例如,在正向太阳主平面上,当太阳天顶角为 40°、观测天顶角为 30°时,缓解了测量太阳辐照度与实际太阳辐照度之间的不匹配,RRMSE 从 19.26% 降至 5.50%。即使在天底观测,RRMSE 也从 12.84 % 降至 5.64 %。总之,MFLD 可以有效缓解辐照度不匹配对 RSIF 提取的影响。这些结果将改进我们对不同观测方向上 GPP 与 RSIF 之间关系的解释。
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来源期刊
Remote Sensing of Environment
Remote Sensing of Environment 环境科学-成像科学与照相技术
CiteScore
25.10
自引率
8.90%
发文量
455
审稿时长
53 days
期刊介绍: Remote Sensing of Environment (RSE) serves the Earth observation community by disseminating results on the theory, science, applications, and technology that contribute to advancing the field of remote sensing. With a thoroughly interdisciplinary approach, RSE encompasses terrestrial, oceanic, and atmospheric sensing. The journal emphasizes biophysical and quantitative approaches to remote sensing at local to global scales, covering a diverse range of applications and techniques. RSE serves as a vital platform for the exchange of knowledge and advancements in the dynamic field of remote sensing.
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