“…The spatial representativeness of a surface site greatly depends on the time scale considered—hours, days, months—as temporal averaging strongly reduces the mismatch between point observation and surrounding area mean [e.g., Zhang et al , ; Wang et al , ; Hakuba et al , ]. Spatial variability in SSR on the subgrid scale is mainly caused by variability in cloud cover and cloud type [e.g., Long and Ackermann , ; Barnett et al , ], as well as altitude, local topography, and surface characteristics surrounding the site [e.g., Hay , ; Tovar et al , ; Riihimaki and Long , ]. The use of multiple sites to approximate a grid cell mean substantially enhances the spatial representativeness [e.g., Barnett et al , ; Li et al , ; Journée et al , ; Hakuba et al , ], but is hardly feasible in most parts of the world due to insufficient coverage by surface sites.…”