Analysis of the Spatial Representativeness of Aerosol Mass Concentration Observations at Regional Background Stationsin the center and east of China

The spatial representativeness (SR) of aerosol mass concentration observations at regional background stations in the center and east of China was assessed using the PM2.5 product from 2010 to 2021，belonging to a series of high-resolution and high-quality datasets of ground-level air pollutants for China. The quality and reliability of the dataset was evaluated using observations at the background stations. And the SR of PM2.5 at Jinsha (JSA), Lin"an (LAN), Shangdianzi (SDZ) and Longfengshan (LFS) regional background station in the center and east of China were assessed. The Concentration Similarity Function (CSF) was applied to calculate the average, the intersection/common and the persistence index of the SR area at the four stations, dividing the 12 study years into three continuous stages (2010—2013, 2014—2017, 2018—2021). Main conclusions are as follows: 1. With the mass concentration relative difference threshold 20%, LFS station has the largest average SR area 22378 km2, followed by JSA (14490 km2), and LAN (9841 km2) and SDZ (7998 km2) adopting the daily average PM2.5 product. 2. As for the intersection/common SR area, LFS station has the largest area (18378 km2), followed by JSA (11915 km2), with SDZ station (5687 km2) and LAN (5476km2) being relatively small. As for the persistence index of the SR area, JSA and LFS are larger than LAN and SDZ. The SR area during 2018—2021 are larger than that during 2014—2017 at the four regional background stations. 3. If the average (intersection/common ) area satisfy the SR area for the air quality regional background stations specified by the Ministry of Ecology and Environment of China (i.e. with the radius 100 km), mass concentration relative difference threshold of the four stations should set to be ≥40% adopting the daily PM2.5 product. 4. The average, the intersection/common, and the persistence index of the SR area assessed adopting the annual average PM2.5 mass concentrations are all larger or better than those assessed adopting the daily average PM2.5 mass concentrations.