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Spatial Variability of offshore internal boundary layers
  • Raghavendra Krishnamurthy,
  • Harindra Joseph Fernando,
  • Qing Wang
Raghavendra Krishnamurthy
University of Notre Dame

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Harindra Joseph Fernando
University of Notre Dame
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Qing Wang
Naval Postgraduate School
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Abstract

The growth of the marine internal boundary layer (MIBL, height ℎ𝑖 ) with the shore-normal distance 𝑥, is a topic of continuing interest because of its applications in coastal dispersion, offshore wind farm siting, coastal air-sea fluxes and in evaporative ducting. Available data on MIBL are only scarce, given the difficulty to measurements and variability of coastal winds. During Coupled Air-Sea Processes and Electromagnetic Research (CASPER)-West campaign, from September 27 to October 27, 2017, an array of instrumentation was deployed on the Californian coast at Point-Mugu and on the research vessel Sally Ride. A state-of-art triple Doppler Lidar system was used to map the flow field up to 500 m in height above sea level and to a distance of ~ 4 kilometers from the coast with a spatial resolution of 30 m. Triple Doppler Lidar provides simultaneous vertical profiles of all three velocity components in the atmospheric boundary layer. A 20 m flux tower was used to characterize the atmospheric surface layer, especially its stability. The temporal variability of MIBL growth measured by the triple Doppler Lidar near the coast every 15 minutes were synthesized by its offshore wind direction and atmospheric stability. Over 5 unique case-studies of MIBL offshore development provided some useful general conclusions on the MIBL growth. Measurements also from a state-of-art motion-stabilized coherent Doppler Lidar and microwave radiometer on Sally Ride also showed the growth of offshore internal boundary layer several kilometers from the coast.