Composite ship track characteristics

The physical and radiative properties of a composite ship track are described from the analysis of 131 ship– ship track correlation pairs collected during the Monterey Area Ship Track experiment. The significant variability of ship tracks around their average characteristics is also described. The nominal environmental conditions for the ship track set are also described. The composite ship track is 296 Ϯ 233 km long, 7.3 Ϯ 6 h old, and averages 9 Ϯ 5 km wide. The ship is, on the average, 16 Ϯ 8 km from of the head of the ship track along the relative wind vector and corresponds to a time of 25 Ϯ 15 min. The set of ship tracks examined in this study formed in marine boundary layers that were between 300 and 750 m deep, and no tracks formed in boundary layers above 800 m. The tracks form in regions of high relative humidity, small air–sea temperature differences, and moderate winds (average of 7.7 Ϯ 3.1 m sϪ1 ). The ambient cloud reflectance in advanced very high resolution radiometer channel 3 (3.7-␮m wavelength) is 11 Ϯ 4%, while the composite ship track value is 14 Ϯ 5%. The relative track brightness is 7 Ϯ 26% and 37 Ϯ 34% for 0.63- and 3.7-␮m wavelengths, respectively.