The spatial representativeness of mixing layer height observations in the North China Plain

To investigate the spatial representativeness of mixing layer height (MLH) observations in the North China Plain (NCP), we performed several successive MLH measurements with ceilometers from 2013 to 2017, and the MLH observation data were analyzed at different measurement scales. Daytime MLH differences among stations increased with increasing observation scale. The relative coefficient (R) and the coefficient of variation (CV) of the hourly daytime MLH decreased and increased from 0.87 and 18.7% to 0.57 and 27.9%, respectively, by enlarging the observation domain from the urban scale (0-20 km) to the synoptic scale (100-300 km). At inter station distances of < 25 km, the daytime MLH values between two sites are highly consistent. At inter-station distances > 25 km but < 60 km, the daytime MLH values at any two sites exhibit obvious differences. Additionally, at inter-station distances > 60 km, the daytime MLH measurements effectively capture the regional MLH distribution characteristics. Therefore, inter-station distances within the range of 25-60 km are useful for detecting whether obvious differences in daytime MLH exist among stations, and an inter-station distance > 60 km is sufficient to obtain daytime MLH observations that represent the regional distribution pattern. Our research results have instructive significance for MLH observation station layouts within the NCP region.