Investigation of the Global Spatio-Temporal Characteristics of Astronomical Seeing.

Astronomical seeing is important for monitoring the atmospheric environment, observation scheduling and management, and selecting astronomical sites. This study first attempts to establish a near-global astronomical seeing map by employing the fifth European Centre for Medium-Range Weather Forecasts Reanalysis (ERA5) data combined with the estimated model. Then, some example sites' results from ERA5 were compared against the astronomical seeing results from the balloon-borne microthermal measurements and the differential image motion monitor (DIMM) instrument. The global astronomical seeing variations exhibit large spatial dependence. The best seeing areas are generally discerned over the mid-latitude regions, consistent with the regions of the European Southern Observatory and Tibetan Plateau. In addition, the astronomical seeing values of the Tibetan Plateau in spring are better than in the other seasons. The site results from ERA5 show that the astronomical seeing values of some example sites are generally consistent with the measurements. Overall, the global astronomical seeing map presented in this study can provide a reference and basis to further understand the astronomy site selection and optoelectronics equipment observation path selection.