Ceilometer-Based Study of the Summer Planetary Boundary Layer in the Central Valley

In the summer months, California’s Central Valley (CV) meteorological setting is characterized by thermally-induced mesoscale flows, complex topographical influences, and synoptic downwelling. The combination of these factors produces abnormally low planetary boundary layer (PBL) heights within the valley. Due to the high spatial and temporal PBLH variation and a scarcity of radiosonde stations in the CV, analysis of the anomalously low PBLHs is limited. This study uses ceilometer aerosol backscatter data to measure the PBLH in the CV. We then correlate the PBLH diurnal cycles with a variety of CV conditions, including Delta breeze impingement, downvalley flow, and along-valley temperature, pressure and moisture gradients. Comparing clear-sky conditions in the summer months, we seek to isolate the cause for the anomalously low PBLH in July and August.