Interaction of the Planetary Boundary Layer Depth With Aerosol and Boundary-Layer Clouds

The depth of the planetary boundary layer (PBL) is driven by surface heating, with strong diurnal and seasonal cycles. Methods to detect the PBL depth from remote sensing instruments such as lidar and infrared spectrometer can take advantage of their high temporal resolution to produce detailed information about PBL development, which in turn has implications for weather, air quality and climate. An algorithm combining two common methods for PBL depth detection (wavelet covariance and iterative curve-fitting) has been evaluated by intercomparison among multiple instruments at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. Radiosonde-derived PBL depths at SGP accounted for over two-thirds the variation in PBL depths from atmospheric emitted radiance interferometer (AERI), and over half the variation in PBL depths from micropulse lidar (MPL). The results are sufficiently robust that the algorithm can be used at other locations that have only one source of atmospheric profiles. The new continuous PBL data set can be used to improve model parameterizations of PBL and our understanding of atmospheric transport of pollutants. Using ground-based MPL profiles from China and the U.S., this study investigates the behavior of the PBL in the presence of aerosol loading, in which the aerosol direct effect would have altitude-dependent consequences, and the interaction of PBL, aerosol and boundary-layer clouds. Figure: PBL depths detected by MPL, AERI and radiosonde, overlaid on MPL backscatter during a nine-day period of typical conditions.