Challenges of Near-Marine Boundary Layer Atmospheric and Turbulence Testing and Modeling

Abstract

Currently there are extensive modeling and measurement capabilities from >100 ft above sea surface to space, but few such capabilities exist for the region extending up to 10 ft above the sea surface. By measuring and characterizing conditions in the marine boundary layer existing below 30 ft above the sea surface such as turbulence and optical attenuation, the communication and imaging capabilities of maritime vessels when operating at or near the surface may be extended and enhanced. Key physical parameters such as absorption, scattering, and turbulence strength (Cn2) along the propagation path have a degree of variability on meteorological conditions (temperature, pressure, humidity) as well optical wavelength. Modeling of the atmospheric environment is thus critical in order to generate a good understanding of optical propagation thorough the atmosphere. Under Naval Engineering Education program with University of Arizona, NUWC is developing a Physics based atmospheric characterization and beam propagation model in time domain to accurately represent Cn2 and beam propagation characteristics through the marine boundary layer. We are developing the capability of near marine boundary layer atmospheric and turbulence measurements and modeling as well as optical laser link testing at outdoor test sites. Measurements are performed with optical laser links (e.g., bit rate error), scintillometer, and particle image velocimetry (PIV) cameras, while turbulence and propagation modeling is achieved using MODTRAN5, ANAM, NSLOT, LEEDR, and WaveTrain software simulation tools. By better understanding the effects of turbulence and Cn2 on optical transmission in the near-marine boundary layer through modeling and experimental measurements, measures can be implemented to reduce the bit error rate and increase data throughput, enabling more efficient and accurate communication links and imaging capabilities.