EVALUATING A SINGLE COLUMN MODEL BLENDING ALGORITHM USING CASPER MEASUREMENTS

Abstract

High vertical resolution profiles of atmospheric state variables are required when one intends to define the evaporation duct, an atmospheric phenomenon that significantly affects surface radar propagation in the atmosphere. Results from mesoscale models have low vertical resolution and cannot resolve the evaporative ducts. Direct measurements by rawinsonde are also problematic at the lowest level, where they are affected by flow distortion and thermal effect induced by the ship. This research evaluated a physics-based blending scheme to append a reasonable surface layer M-profile to soundings profiles. The “blending” technique can be used to extend the measured or model refractivity profiles down to the surface layer to include the evaporation duct. The basic framework used COAMPS in a single column mode with high vertical resolution and thus was capable of resolving the evaporation duct. In this study, results from the single column model (SCM) are compared to profiles from tethered balloon measurements on small boats, an effort of the Coupled Air-Sea Processes and Electromagnetic Ducting Research project.