4.3 Marine Atmospheric Boundary Layer Profiling during the CASPER Campaign

Tuesday, 16 August 2016: 9:00 AM
Lecture Hall (Monona Terrace Community and Convention Center)
A.J. Christman, University of Notre Dame, Notre Dame, IN; and L. S. Leo, E. D. Creegan, Q. Wang, C. Hocut, H. J. S. Fernando, and D. Grober

Intense boundary layer profiling was performed during the CASPER field campaign (12 October – 6 November 2015) on two different research vessels and on the coast at the Army Corps of Engineers Field Research Facility (FRF) in Duck, NC. Remote sensors, radiosondes and tethered balloon platforms were deployed, and measurement inter-comparisons were conducted for select cases. The motivation was to provide background atmospheric data in support of electromagnetic propagation measurements and modeling. As part of these efforts, both a scanning Doppler lidar and a profiling microwave radiometer were deployed aboard the R/V Atlantic Explorer to sample the lower MABL. A highlight was the testing and performance assessment of Motion Picture Marine's Perfect Horizon lidar-stabilizing platform. Alongside these measurements, high-frequency launches of radiosondes as well as tethered balloon profiles were made, which enabled regular validation of lidar profiles. Together, these systems sampled near-continuously for the duration of the deployment.

The motion-stabilized lidar was programmed to operate in a multi-scan pattern strategy to measure vertical profiles of horizontal and vertical wind speeds and wind direction in the lower 1km of the boundary layer at approximately a 5-minute resolution. The radiometer complemented these data with measurements of temperature and relative humidity profiles up to 10km on sub-minute time scales. The rms velocities were also obtained using the Lidar data. Radiosondes were released in an up/down sampling mode at overall rates of 7-8 per day with local periods of up to once per hour, while profiling using the Tethered Lifting System (TLS) was conducted for periods of nearly 1 hour, 3-4 times per day under favorable wind conditions. A good agreement was found between measurements by different platforms.

Daily measurement schedules were arranged such that two research vessels transited a pre-determined east-west pathway off the coast. Findings from a subset of these transits will be presented, with an emphasis on the development of horizontal gradients of atmospheric parameters at land-ocean and hydro-physical discontinuities (e.g. Gulf Stream). A discussion of how these gradients affect canonical marine boundary layer theories will be given.

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