Comparisons of Planetary Boundary Layer Height from Ceilometer with ARM Sounding Data

The planetary boundary layer (PBL) depth is an important parameter influencing a variety of atmospheric processes. PBL top height (PBLHT) can be determined from several methods including methods using temperature, humidity, and/or wind profiles from radiosonde measurements, and methods using gradients of aerosol backscatter intensity from lidar measurements. Radiosonde measurements provide accurate temperature and water vapor profiles, but they exist only a few times per day. Lidar measurements provide high temporal resolution aerosol backscattering profiles and are available at all Atmospheric Radiation Measurement (ARM) sites and most ARM field campaigns. The Vaisala ceilometer (CL31) has built-in software that uses an enhanced gradient method to retrieve PBLHT. However, the robustness of the retrieved PBLHT has not been validated under various atmospheric conditions. In this study, we compare multiple years of PBLHT retrievals from ceilometer with that from radiosonde data at the ARM Tropical Western Pacific (TWP), Southern Great Plains (SGP), Eastern North Atlantic (ENA), and North Slope of Alaska (NSA) sites. The locations of these sites cover from the tropics to the polar regions and include both land and water surfaces. Our preliminary analyses show that correlation coefficients and root-mean-square errors between ceilometer and sounding PBLHTs change dramatically over different sites, indicating that the surface type impacts the quality of the retrieved PBLHTs from ceilometer. Retrieved PBLHTs over the land surface generally has higher correlation coefficients than the water surface. At each given site, the correlation coefficients and root-mean-square errors also change greatly at different times of the day and under different boundary layer stabilities and aerosol loadings.