Abstract
Photosynthetically active radiation (PAR) is a fundamental physiological variable for research in the ecological, agricultural, and global change fields. In this study, we produced a 35-year (1984–2018) high-resolution (3 h, 10 km) global gridded PAR dataset using an effective physical-based model. The main inputs of the model were the latest International Satellite Cloud Climatology Project (ISCCP) H-series cloud products, MERRA-2 aerosol data, ERA5 surface routine variables, and MODIS and CLARRA-2 albedo products. Our gridded PAR product was evaluated against surface observations measured at seven experimental stations of the SURFace RADiation budget network (SURFRAD), 42 experimental stations of the National Ecological Observatory Network (NEON), and 38 experimental stations of the Chinese Ecosystem Research Network (CERN). Instantaneous PAR was validated against SURFRAD and NEON data; mean bias errors (MBE) and root mean square errors (RMSE) were, on average, 5.8 W m−2 and 44.9 W m−2, respectively, and correlation coefficient (R) was 0.94 at the 10 km scale. When upscaled to 30 km, the errors were markedly reduced. Daily PAR was validated against SURFRAD, NEON, and CERN data, and the RMSEs were 13.2 W m−2, 13.1 W m−2, and 19.6 W m−2, respectively at the 10 km scale. The RMSEs were slightly reduced when upscaled to 30 km. Compared with the well-known global satellite-based PAR product of the Earth's Radiant Energy System (CERES), our PAR product was found to be a more accurate dataset with higher resolution. This new dataset is now available at https://doi.org/10.11888/RemoteSen.tpdc.271909 (Tang, 2021).
Highlights
Plants rely on chlorophyll to absorb solar radiation in the visible wavelength range (400–700 nm) for photosynthesis (Huang et al, 2020), and sunlight in this band is commonly referred to as photosynthetically active radiation (PAR)
We evaluated the performance of our PAR product using in-situ observations measured across three experimental observation networks in the United
In-situ observations from three networks were used to evaluate the performance of our ISCCP-ITP PAR product at instantaneous and daily scales
Summary
Plants rely on chlorophyll to absorb solar radiation in the visible wavelength range (400–700 nm) for photosynthesis (Huang et al, 2020), and sunlight in this band is commonly referred to as photosynthetically active radiation (PAR). PAR is the source of energy for biomass formation and may directly affect the growth, development, yield, and product quality of vegetation (Zhang et al, 2014; Ren et al., 2021), modulating energy exchange between Earth’s surface and the atmosphere (Zhang et al, 2021). A high-quality PAR dataset is indispensable for studies of ecosystems, agriculture, and global change (Frouin et al, 2018). Measurements of PAR are not routinely conducted at weather stations or radiation stations. PAR is not routinely observed at the Baseline. Surface Radiation Network (BSRN, Ohmura et al, 1998) or at the China. Meteorological Administration (CMA, Tang et al, 2013) weather/radiation stations. Long-term PAR observations are only provided by a few ecological experimental observation networks, such as the Chinese Ecosystem Research Network (CERN, Wang et al, 2016), the AmeriFlux network (https://ameriflux.lbl.gov/), the SURFace
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