CN2 model to calculate the micrometeorological influences on the refractive index structure parameter

This paper presents the CN2 model for calculating the micrometeorological influences on the refractive index structure parameter. The CN2 model is a semi-empirical algorithm developed by the U.S. Army Research Laboratory to provide realistic values for the refractive index structure parameter over land given two vertical levels of conventional wind speed, temperature, and humidity data as input. The CN2 model is based on the structure function formulations of Tatarski. Equations for the real index of refraction are expressed in terms of temperature, pressure, and moisture (preferably the conserved elements potential temperature and specific humidity). Calculations of micrometeorological profile structure are carried out via Monin–Obukhov theory for the surface layer. Model results can be derived for unstable, stable, and near-neutral atmospheric conditions. The CN2 model algorithm is validated in comparison to optical scintillometer data collected at 2 m above ground level over a 450 m path. The paper reported here contains technical and user’s guide information on the CN2 model.