LKB-Based Evaporation Duct Model Comparison with Buoy Data

Abstract

A wave-riding catamaran with a mast-traveling sensor package (profiling buoy) was developed to make fine-scale atmospheric measurements within the first meter above the ocean surface. These measurements are used to generate time-averaged modified refractivity (M) profiles that are then compared with those determined from four evaporation duct models based on the surface layer theory of Liu, Katsaros, and Businger (LKB). Model inputs are derived from measurements from masts on the R/V Chessie and from a tethered sea surface temperature buoy. Because electromagnetic propagation is critically dependent on the M-profile slopes, different analytical techniques are employed to compare the curvature of the model profiles with that of the profiles measured by the profiling buoy. One comparison criterion was to use the rms M slope difference between the model and a curve fit to the buoy profile data. Another analytical technique was to use the rms M difference after mean M removal between the model and the buoy profiles. Using these criteria for comparison of these models with the data seems to indicate that the model-derived profiles may be missing some phenomena in the surface layer such as wave effects. Overall, however, the shapes of the measured M profiles showed log-linear characteristics near the surface. One interesting result is that each model was better at approximating the M-profile curvature for stable than for unstable conditions.