A zero-order-closure turbulent flux-conservation technique for blending refractivity profiles in the marine atmospheric boundary layer

Abstract

Recent advances in mesoscale numerical weather prediction (NWP) models have supported four-dimensional (4D) radio-frequency (RF) propagation modeling in challenging heterogeneous refractive marine environments. Numerical weather prediction models typically provide a vertical profile of refractivity every 1 km to 3 km horizontally in the domain of interest for each hour in a 48-hour forecast. Due to surface roughness and turbulence constraints, these profiles extend from the stratosphere to within 5 m to 10 m of the sea's surface. Because of strong evaporation at the sea's surface, significant impacts on RF system performance can be induced by refractivity gradients in the first 10 m above sea level (ASL). Historically, the lower-layer refractivity profiles have been calculated using Monin-Obukhov-Similarity-(MOS) based turbulence models. This dual-model approach requires a robust technique for blending on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> profiles per forecast hour without creating non-physical refractivity artifacts. This paper describes a zero-order-closure turbulent-flux technique for blending numerical weather prediction and Monin-Obukhov Similarity refractivity profiles, and presents the results of a multi-wavelength data-comparison process.