The spatial and temporal variability of the clear convective boundary layer at the ARM SGP supersite

The convective boundary layer (CBL), also known as the mixing layer, constitutes the critical lower segment of the atmosphere that significantly influences daily human activities. The growing demand for precise weather forecasts is driven by the requirements of agriculture, transportation, and routine societal functions. To enhance the understanding of CBL, this study investigates spatiotemporal variability in the CBL and its controlling factors using four-year Doppler Lidar, surface flux, and profiling measurements at five ARM Southern Great Plains sites within a 100 km radius. This investigation utilizes data collected exclusively under clear-sky conditions or scattered low-cloud conditions. Results reveal significant spatial differences in CBL evolutions. Daily Mixing Layer Heights (MLHs) vary up to 1 km (30% of the mean) in late afternoon. There is a clear east-west contrast: western sites (C1, E32, E37) exhibit higher summer MLH (1.9–2.1 km) and vertical velocity variances (1.0–1.2 m²/s²) than eastern sites (1.6–1.8 km), reversing in winter. Temporally, MLH peaks at 70% of the sunrise-sunset interval, lagging heat flux (HF) peaks at 50%; seasonal MLH maxima lag HF by ~1-month, influenced by nighttime PBL properties. HF and Lower Tropospheric Stability are the main influential factors for CBL, but site-specific dependencies highlight the critical roles of local factors, underscoring the need for including them in CBL modeling.