Photosynthetically available radiation (PAR) is essential for the photosynthesis processes of land plants and aquatic phytoplankton. Satellite observation with different diurnal frequencies (e.g., high frequency from geostationary satellites and low frequency from polar-orbit satellites) provides a unique technique to monitor PAR variation on large tempo-spatial scales. Owing to different climatic characteristics, different regions may require different observation frequencies to obtain accurate PAR estimation, but such requirements are still poorly known. Here, based on Advanced Himawari Imager (AHI) high-frequency (10-min) observation data from the geostationary satellite Himawari-8, we investigated the influence of diurnal observation frequency on the accuracy of PAR estimation and provided the minimal observing frequency to get high accurate PAR estimation in the AHI coverage area. Our results revealed a remarkable difference in the requirements for the diurnal observation frequency in both spatial and temporal distributions. Overall, high-latitude regions need a higher observing frequency than low-latitude areas, and winter half-years need higher observing frequency than summer half-years. These results provide a basis for designing satellites to accurately remote sensing of PAR in different regions.