Recently, DING Xiaosong, a doctoral student in our laboratory, published a research paper titled "Requirement on the diurnal observation frequency for satellite remote sensing of photosynthetically available radiation" on Optics Express. The corresponding author is researcher HE Xianqiang of our laboratory.
The solar energy reaching the earth's surface in the 400–700 nm wavelength region is called photosynthetically available radiation (PAR), which can be used by land plants, marine phytoplankton, and other primary production organisms in the photosynthesis process. and plays an important role in the carbon sequestration process. Satellites with different orbital altitudes can provide different observation frequencies within a day (for example, geostationary orbiting satellites can achieve multiple observations per day, and polar orbiting satellites can achieve one observation per day). Currently, PAR remote sensing products based on polar-orbiting satellites estimate daily integrated PAR based on a single observation, without considering the influence of changes in meteorological elements within the day, which inevitably leads to large uncertainties (Figure 1). Based on the photosynthetically active radiation (PAR) remote sensing products of geostationary satellites (Himawari-8/AHI) and polar-orbiting satellites (AQUA/MODIS), this paper systematically studies the impact of different intraday observation frequencies on PAR remote sensing estimates, and provides AHI coverage The minimum intraday observation frequency for regional high-precision PAR estimation. The results show that there are significant differences in space and time in intraday observation frequency requirements. High latitude sea areas require higher intraday observation frequencies than low latitude sea areas, and winter half of the year requires higher intraday observation frequencies than summer half of the year. This study can provide a reference for understanding the uncertainty of PAR remote sensing assessment in different regions.
Figure 1 Intraday variations of instantaneous PAR (iPAR), solar zenith angle (SOZ) and cloud optical thickness (COT) at different latitudes of AHI along 180OE during the summer solstice, autumnal equinox and winter solstice in 2019
Liu, D., Y. Bai, X. Q. He, C. T. A Chen, et al. Changes in riverine organic carbon input to the ocean from mainland China over the past 60 years. Environment International, 2020, 134:105258.
