Ship Tracks - Ship Tracks Study

Ship Tracks Study

In 1965, the first "anomalous cloud lines" were observed in images from the TIROS VII satellite. It was hypothesized that the most likely cause was from the exhaust from ships. Many studies since have confirmed the cause, and they are now referred to as ship tracks. Scientists soon realized that the climatic impacts from aerosols could have a large effect on climate through the indirect effect, and that ship tracks provided an excellent laboratory for their studies.

Scientists who study how human-produced aerosols affect cloud formation observe ship tracks because in most urban areas, they are unable to discern exactly how pollutants contribute to forming clouds because the atmosphere over the land is too tumultuous. In contrast, ships release their exhaust into the relatively clean and still marine air, where the scientists have an easier time of measuring the effects of fossil fuel emissions on cloud formation.

In general, the air above the oceans suffers from less turbulence and convection than the air above land. The lower atmosphere is especially calm over the eastern Pacific in the summertime due to a layer of hot air that settles in 500 to 700 meters above that region of the ocean. This effect creates a temperature inversion, placing a cap on the cooler air below, trapping pollutants and water vapor. While the inversion is responsible for the smog that reduces air quality in Los Angeles, it also allows for the formation of long lasting ship tracks. The particles billowing from ships' smokestacks enter the air above the eastern Pacific and create long, thin clouds that remain there for days.