Measurements of IR propagation in the marine boundary layer during the September 2011 SQUIRREL trial

A multinational field trial (SQUIRREL) was performed at the Eckernförder Bucht, in the Baltic Sea, during September 2011 to study infrared ship signature and atmospheric propagation effects close to the sea surface in a cool environment. In this paper mid-wave infrared camera recordings of ship-mounted sources are analyzed. The camera was positioned about 6 m above mean sea level. Several meteorology stations - mounted on land, on a pier and on a buoy - were used to characterize the propagation environment, while sensor heights were logged continuously. Both sub- and superrefractive conditions were studied. Measurements are compared to results from an earlier field trial performed at Chesapeake Bay, in 2006, during warm and humid atmospheric conditions. The ship-mounted sources - two calibrated blackbody sources at 200 °C and 100 °C - were used to study contrast intensity and intensity fluctuations as a function of distance. The distance to the apparent horizon is also determined. Measurement results are compared to results from the IR Boundary Layer Effects Model (IRBLEM), and good agreement is found.