Synoptic and Mesoscale Variability in Convective Boundary Layer Depth Observations from Dual-Polarization WSR-88D Radars

The convective boundary layer (CBL) is one of the most important and variable layers in the atmosphere, yet observations of the CBL have been limited. Recent results show that the dual-polarization WSR-88D radars can observe CBL depth using differential reflectivity observations on most days with observations available every 10 min or less. We apply a CBL depth tracking method to observations from 48 WSR-88D dual polarization radars spread across CONUS for 2014 and 2022. Results indicate that mean monthly CBL depth over CONUS is smallest in December at 632 m and largest in June at 1606 m. Objective analyses of daily maximum CBL depths show large horizontal variability with synoptic and mesoscale processes contributing to this variability. CBL depths are deeper in the warm sector of midlatitude cyclones compared to surrounding regions, with some days showing anomalies in maximum daily CBL depth of over 1000 m in the warm sector. Mesoscale processes such as lake and sea breezes and precipitation also influence CBL depths. The time of maximum CBL depth shifts throughout the year, being earliest in the winter months and over an hour later in the summer months with regional variations. CBL depth increases most rapidly 1–3 h prior to local noon, with decreases in CBL depth starting 3 h after local noon. Calculating CBL depth routinely from the WSR-88D network will be valuable for air quality and aviation forecasts, model verification, and data assimilation.