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A multinational field trial (SAPPHIRE) was performed at the Chesapeake Bay, USA, during June 2006 to study infrared ship signature and atmospheric propagation effects close to the sea surface in a warm and humid environment. In this paper infrared camera recordings of both land and ship mounted sources are analyzed. The cameras were positioned about 4 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 earlier field trials performed in Norway during typical North-Atlantic atmospheric conditions (cool air with little water content), and differences between medium wave and long wave infrared are emphasized. The ship mounted source - a calibrated blackbody source - was used to study contrast intensity and intensity fluctuations as a function of distance. The distance to the apparent horizon is also determined. In addition, normalized variance of intensity for land based sources has been calculated for a number of cases and these values can easily be converted to refractive index structure constant C 2 n -values. Measurement results are compared to results from the IR Boundary Layer Effects Model (IRBLEM).

We present results from infrared imaging experiments, performed under hot and humid conditions at Chesapeake Bay, Maryland, USA in the summer of 2006. Specifically, the objective was to study the intensity of the exhaust gases from a ship at different distances. In particular there is an interest to quantify the intensity decrease of the plume with distance and correlate this with simulations of atmospheric transmission. For this purpose the ship ran a predetermined course making broad-side passes at predetermined distances from the shore-based IR camera as part of the course. The distances were 1.6, 2.4, 3.2, 4, 6, and 8 km. The cameras are sensitive in the 3 - 5 μm and 8 - 12 μm wavelength ranges. Digital recordings were made during the ship broad-side passes. It is challenging to identify gas cloud pixels against a background because the pixels are not necessarily clustered. We present a statistical method to identify the gas cloud pixels, calculate their average intensity, and determine the contrast between the gas pixels and the background pixels as a function of distance. The contrast versus distance data are then compared with simulations using standard atmospheric transmission software.

Measurements of the spectral radiance of the sky and the sea, taken near Halifax during the September 2001 SIMVEX trial, indicated that the use of user defined atmospheric profiles, i.e. high altitude atmospheric contributions, were necessary in order to obtain agreement between measurements and results from simulations using atmospheric radiance codes. This paper analyzes data obtained under hot and humid conditions during the SAPPHIRE trial at Chesapeake Bay, Maryland, USA, in the summer of 2006. Digital recordings of the sea and sky background were made using cameras sensitive in both the 3 - 5 μm and 8 - 12 μm wavelength range. The center of the field of view of the cameras was pitched from -5 to +15 degrees. In parallel with the imaging experiments, spectrometric data was collected at the same time. In addition, many different types of meteorological data were collected. Measurements of the vertical radiance profile near the horizon will be compared with simulation results from ShipIR using various meteorological input parameters.