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 profi le 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 profi les 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, signifi cant impacts on RF system performance can be induced by refractivity gradients in the fi rst 10 m above sea level (ASL). Historically, the lower-layer refractivity profi les have been calculated using Monin-Obukhov-Similarity-(MOS) based turbulence models. This dualmodel approach requires a robust technique for blending on the order of 3 10 profi les per forecast hour without creating non-physical refractivity artifacts. This paper describes a zero-order-closure turbulent-fl ux technique for blending numerical weather prediction and Monin-Obukhov Similarity refractivity profi les, and presents the results of a multi-wavelength data-comparison process.