Observations of Morning PBL Transitions Using Rotary-Wing Unmanned Aircraft Systems

The University of Oklahoma (OU) CopterSonde is a rotary-wing unmanned aircraft system (rwUAS) designed to make high resolution thermodynamic and kinematic measurements of the atmosphere. Continuous vertical profiles with the CopterSonde were conducted at the Kessler Atmospheric and Ecological Field Station (KAEFS) in central Oklahoma on several occasions in both the wet and dry seasons to capture the evolution of the early morning planetary boundary layer (PBL). These profiles take place on the order of once every 10-20 minutes, and they extend to an altitude of 2500 feet above ground level (AGL), and eventually 4000 feet AGL. Furthermore, KAEFS is outfitted with an Oklahoma Mesonet station, a Doppler wind lidar (DL), and a microwave radiometer (MWR) to provide platform intercomparisons and validations.

This presentation will focus initially on the CopterSonde design and sensor integration as part of an ongoing calibration/validation objective. In particular, recent results have shown that a UAS can modify the environment it is sampling, necessitating caution when deciding sensor placement. Following this discussion, attention will be given to ideal sampling strategies for combining analysis with other ground-based remote sensors. Results from the morning profiles will then be discussed, specifically addressing comparisons between theory and observations from the rwUAS, DL, MWR, and instrumented tower. Additionally, insights to how seasonal variations in temperature, moisture, and winds are related to their associated fluxes will be explored. These data also provide the ability to determine the vertical extent of the PBL affected by the rapidly changing nature of surface heat and moisture fluxes. The ability of the CopterSonde to fly to such altitudes and collect in-situ data provides a unique perspective on boundary layer processes, complementing the continually-scanning surface-based sensors.