Surface-Based PBL Height Retrievals from a Collocated Ceilometer, Lidar, and Radar Wind Profiler in Context of a Global PBL Observing System

It was well established in the NASA Incubation Study Team Report that there is a critical need for a global planetary boundary layer (PBL) observing system with contributions from surface-based, suborbital, and space-based observations as well as modeling and data assimilation systems. Networks of multiple surface-based instruments (e.g. lidar, ceilometers, radar wind profilers, microwave radiometers) are unique in that they can provide high vertical and temporal resolution retrievals of the PBL height and entrainment zone with greater measurement sensitivity in the PBL compared to spaceborne sensors. Furthermore, densely distributed surface networks are important when requirements for spatial resolution vary with geographical location. For example, satellite measurements may not be able to capture large spatial gradients in PBL structure. Thus, surface-based observations provide essential “ground truth” and program of record needed to validate the proposed incubator space-based instruments and modeling/DA systems which can provide true global coverage and observations in locations not possible with surface-based networks.

In this presentation, we use results of an intercomparison of surface-based PBL height retrievals from a collocated radar wind profiler, a lidar and a ceilometer at the Howard University Beltsville Campus in Maryland. The PBL height retrievals are derived using the same algorithms as used by the Global Radar Wind Profiler-PBL Height (GRWP-PBLH), Micro Pulse Lidar Network (MPLNET) and Unified Ceilometer Network (UCN), respectively. We show case studies and detailed analysis from two month-long measurement periods (July 2011 and March 2020) to discuss the limitations and errors associated with the retrievals from each instrument and the synergy among them.

We compare the surface-based retrievals from this intercomparison to space-based PBL height retrievals from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), Ice, Cloud, and land Elevation Satellite-2 (ICESat-2), and Global Navigation Satellite System-Radio Occultation (GNSS-RO) to illustrate similarities and differences among these complementary platforms. Finally, reanalyses from Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) and ancillary data from nearby meteorological stations are used to provide context in interpreting variability in the PBL height due to different conditions.