High-Frequency Observations of the Complex Terrain Boundary Layer during Perdigão

In the spring of 2017, the Perdigão Program instrumented a unique, parallel ridge mountain in Perdigão, Portugal in unprecedented spatial and temporal resolution using traditional tower mounted sensors, instrumented aerial platforms, and remote sensing instrumentation. One of the unique aspects of Perdigão is that measurements of turbulence in the atmospheric boundary layer were not limited to ground based towers which typically restrict the phenomena that can be sampled, including low level jets, rotors, and entrainment. During Perdigão, the Army Research Laboratory and University of Colorado operated a Tethered Lifting System (TLS) equipped with an instrumentation package that includes a hot-wire anemometer and cold-wire to measure velocity and temperature fluctuations at 1 KHz, and temperature, pressure, humidity and wind speed measurements at lower frequencies for dynamic calibration of the hot-wire/cold-wire. Each TLS performed over 100 profiles of the atmospheric boundary layer during diverse background meteorological conditions which provided the unique opportunity to characterize the turbulent structure of the boundary layer. Coincident radiosonde profiles provided data for an inter-comparison with a traditional, albeit low-frequency platform. Preliminary results that demonstrate the TLS capabilities will be presented for several flow regimes including quiescent conditions in which morning and evening transitions occurred, and synoptic forced conditions in which jets formed at the exit of a gap in the mountain topography and rotors were observed.