Assessment of five different methods for the estimation of surface photosynthetically active radiation from satellite imagery at three sites – application to the monitoring of indoor soft fruit crops in southern UK

Abstract

Abstract. This paper assesses several methods for the retrieval of Photosynthetically Active Radiation (PAR) from satellite imagery. The results of five different methods are compared to coincident in-situ measurements collected at three sites in southern UK. PAR retrieval methods are separated into two distinct groups. The first group comprises three methods that compute PAR by multiplying the satellite-retrieved solar broadband irradiance at the surface (SSI) by a constant coefficient. The two methods in the second group are based on more sophisticated modelling of the radiative transfer in the atmosphere involving advanced global aerosol property analyses and physically consistent total column water vapour and ozone produced by the Copernicus Atmosphere Monitoring Service (CAMS). Both methods compute a cloud modification factor from satellite-retrieved SSI. The five methods have been applied to two satellite-retrieved SSI datasets: HelioClim-3 version 5 (HC3v5) and CAMS Radiation Service (CAMS-Rad). Except at the seashore site, Group 2 methods combined with the cloud extinction from the HC3v5 dataset deliver the best results with small biases of −5 to 0 µmol m−2 s−1 (−1 % to 0 % relative to the mean of the measurements), root mean square errors of 130 µmol m−2 s−1 (28 %) and correlation coefficients exceeding 0.945. For all methods, best results are attained with the HC3v5 data set. These results demonstrate that all methods capture the temporal and spatial variability of the PAR irradiation field well, although several methods require a posteriori bias adjustments for reliable results. Combined with such an adjustment, the Udo et Aro method is a good compromise for this geographical area in terms of reliability, tractability and its ability to run in real-time. Overall, the method performing a spectral discretization in cloud-free conditions, combined with the HC3v5 dataset, outperforms other methods and has great potential for supporting an operational system.

Smart Approaches for Evaluating Photosynthetically Active Radiation at Various Stations Based on MSG Prime Satellite Imagery

“…This work extended the validation initiated in 2018 [32]. In the previous work, five methods to assess PAR from satellites were developed and evaluated at three sites in the United Kingdom.…”

“…This paper aimed to check whether the conclusion previously drawn could be extended to a much wider set of sites in Europe, Africa, the Middle East, and South America. In Thomas et al [32], two surface solar irradiance (SSI) resources, HelioClim-3 version 5 (HC3) and the Copernicus Atmosphere Monitoring Service radiation product in allsky conditions (CAMS-Rad), were utilized. Both resources relied on CAMS McClear for cloud-free conditions [23,25].…”

“…In line with Thomas et al [32], we first deployed the approach of Opálková et al [38] as an adaptation of the quality control procedure of Korany et al [39], which was applied to broadband irradiance measurements. This quality control turned out to be well-suited to the 30 min PAR measurements, for instance, at Aberystwyth University and Abbotts Hall, serving as a reference.…”

“…Therefore, the purpose of this article was to assess and inter-compare the performance of both previously tested and newly developed methods for estimating surface PAR in Europe, Africa, the Middle East, and South America. In addition, this study expanded the validation of five recent methods developed by Thomas et al [32], which were limited to three sites located in the southern UK. Newly developed methods rely on modeling the attenuation of PAR due solely to clouds.…”

Photosynthetically Active Radiation Separation Model for High-Latitude Regions in Agrivoltaic Systems Modelling

“…Therefore, as a work-around, several authors have suggested a variety of models to estimate the different components of PAR. PAR components can be estimated using atmospheric radiative transfer models (ARTM), e.g., Bird and Riordan (1986), Gueymard (1995) or Emde et al (2016) and methods derived from these, e.g., Wandji et al (2019) or Thomas et al (2019). However, since ARTM is associated with high complexity and using it demands much knowledge in atmospheric sciences, most of the models are empirical.…”