We evaluate a similarity-based optical turbulence model that estimates diurnal values for Cn2 from easily obtained local terrain and environmental information by comparing it with scintillometer data taken at the Army Research Laboratory’s A_LOT facility in Adelphi, Maryland. The A_LOT facility is characteristic of many planned urban sites for free-space laser communication. One end of the test site is on top of a two-story building, and the other end is a water tower about 70 meters high. This comparison examines the effects of the asymmetric location, such as the non-uniform height above ground and surface roughness length. We found that by emphasizing the terrain type directly in front of the receiver and assuming the height above ground to be the height of the receiver, model results compare favorably with experimental data.
We present an optical turbulence model that has evolved from the PAMELA model. After a preliminary report in SPIE 2003 it became apparent that more data was needed to refine this adaptive model. This led us to take twelve months of over-land data (~100 meters pathlength) at the Chesapeake Bay Detachment of the Naval Research Lab. We present data throughout the year with varying environments with comparison with the model prediction. Our recent modification includes segmenting the windspeed to 3 sections, morning, afternoon, and night for better fitting. This is an attempt to incorporate variable wind speed into the model which is known to contribute significantly to the turbulence in the atmosphere. In addition, we present preliminary results from the over-the-bay data (10 km pathlength).