4.6 Air-sea exchange influence on boundary layer moisture and atmospheric refraction

Tuesday, 16 August 2016: 9:45 AM
Lecture Hall (Monona Terrace Community and Convention Center)
Tracy Haack, NRL, Monterey, CA; and Q. Wang

The exchange of latent heat at the sea surface is often overestimated by COAMPS surface flux parameterization scheme in comparison with field observations. This feature introduces moisture into the lower atmosphere tending to weaken the vertical moisture lapse in the model. Typically vapor pressure is the dominate parameter in the refractivity equation, and its vertical distribution dictates how the atmosphere refracts or bends electromagnetic (EM) wave energy. The EM wave can propagate well beyond the horizon in trapping conditions denoted by a sharp decrease with height in refractivity commensurate with that of moisture, or alternatively it can have a much shorter propagation path in sub-refractive conditions associated with a sharp increase with height. Our aim is to improve the representation of latent heat flux in COAMPS with validation from observed flux values and vertical gradients of moisture thereby more accurately representing atmospheric refractivity and the prediction of EM propagation. The latter is of primary importance to the Navy because the performance of operational sensors and communications can be significantly degraded or enhanced due to strong sensitivity of EM signals to the environment. To advance the modeling capability, we evaluate the high resolution air-sea coupled COAMPS forecasts undertaken as part of the CASPER field experiment off of Duck, North Carolina (Oct 2015), utilizing the collection of environmental and propagation measurements available from the three week-long campaign.
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