This short contrail sublimated rapidly behind an airplane crossing above a field of crepuscular rays, as seen from the west lawn of the National Weather Center. I used “sublimated” instead of “evaporated”, because even as hot and moist as the engine exhaust was, its condensation crystallized to ice within a second or two in the surrounding bitter-cold air of double digit below zero (F). The ice crystals then sublimated (direct evaporation of ice) much faster than most visible contrails, due to the dryness of the surrounding air mass that got mixed turbulently into the plume. Sunset is a good time to photograph contrails, as they often contrast in light markedly from surrounding clouds and sky. Here, sunlight was passing through less of the atmosphere to reach the far-higher airplane and its exhaust (a losing less of its blue light) than it was before reddening the edges of the rampart of towering cumuli lining our horizon. The relative positioning, length and angle of travel for the contrail were strikingly similar to the original “Little Contrail” shot on slide film, eleven years earlier.
Norman OK (30 May 10) Looking WNW
35.1818, -97.4407Little Contrail and Crepusculars
This short contrail sublimated rapidly behind an airplane crossing above a field of crepuscular rays, as seen from the west lawn of the National Weather Center. I used “sublimated” instead of “evaporated”, because even as hot and moist as the engine exhaust was, its condensation crystallized to ice within a second or two in the surrounding bitter-cold air of double digit below zero (F). The ice crystals then sublimated (direct evaporation of ice) much faster than most visible contrails, due to the dryness of the surrounding air mass that got mixed turbulently into the plume. Sunset is a good time to photograph contrails, as they often contrast in light markedly from surrounding clouds and sky. Here, sunlight was passing through less of the atmosphere to reach the far-higher airplane and its exhaust (a losing less of its blue light) than it was before reddening the edges of the rampart of towering cumuli lining our horizon. The relative positioning, length and angle of travel for the contrail were strikingly similar to the original “Little Contrail” shot on slide film, eleven years earlier.
Norman OK (30 May 10) Looking WNW
35.1818, -97.4407