Further improvements and validation for the Navy Atmospheric Vertical Surface Layer Model (NAVSLaM)

The Navy Atmospheric Vertical Surface Layer Model (NAVSLaM) is the official U.S. Navy model for characterizing near-surface radio-frequency refractivity over the ocean, which is usually dominated by the presence of an evaporation duct. NAVSLaM employs Monin-Obukhov similarity theory (MOST) to describe the air-sea fluxes and the near-surface profiles of temperature and humidity, which in turn are used to compute modified refractivity profiles for input to propagation models. The employment of MOST theory for this purpose is dependent upon the use of empirically determined dimensionless profile functions for temperature and humidity, and also wind speed. The forms of these empirical profile functions have a dramatic impact on the behavior of surface-layer models, such as NAVSLaM, in describing the evaporation duct. Over the last 50 years and more, researchers have presented a multitude of different formulations for these profile functions, based primarily on field experiments conducted over land or ice.