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Ship Tracks Off Coast of California and Effects on Climate

34.0N 124W

June 7th, 2013 Category: Climate Change, Clouds MODISTerra

USA – June 6th, 2013

The track of large ships is sometimes visualised by a trail of shallow stratus clouds. These clouds, known as ‘ship tracks’, form in the wake of ships and are remarkably long-lived. They typically are between 0.5-5 km wide, i.e. wide enough to be seen in visible satellite imagery. Here, several can be seen southeast of California, USA.

Sometimes a ship track appears as a band of enhanced cloud thickness embedded in stratus. Ship tracks are due to cloud condensation nuclei (CCN) in the ship’s exhaust. They are most likely in a near-saturated environment that is otherwise depleted of CCN. Such environment is very common in the marine boundary layer over the subtropical highs. Over these large, quasi-stationary highs, the boundary-layer air is divergent, making it unlikely to draw in CCN-rich continental air.

The nature and climatic effect of ship tracks has been investigated off the central California coast. Ship tracks increase the albedo, yet have very little effect on the long-wave radiation balance, because they are so shallow. Therefore ship-tracks tend to cool the global climate, although the magnitude of this effect is likely to be small (click here for more information).

Arch of Dust from Morocco to Iberian Peninsula and Ship Tracks

31.9N 13.1W

June 25th, 2012 Category: Clouds, Dust Storms

Dust by Spain and Morocco - June 25th, 2012

A large arch of dust can be seen blowing northwestward over Morocco (lower right quadrant), off the coast of western Africa and over the Canary Islands (center of bottom edge), then curving northeastward towards the Iberian Peninsula (upper right quadrant). Also of note in the upper right quadrant are ship tracks, visible as three roughly parallel lines radiating outwards from a single point near the top edge. Ship tracks are clouds that form around the exhaust released by ships into the still ocean air.

Ship Tracks Over Pacific Ocean Off Coast of California, USA

32.0N 122.6W

June 5th, 2012 Category: Clouds

USA - June 1st, 2012

The criss-crossed patterns of lines in the clouds off the coast of California, USA, are an atmospheric phenomenon known as ship tracks. These are clouds that form around the exhaust released by ships into the still ocean air.

Water molecules collect around the tiny particles (aerosols) from exhaust to form a cloud seed. More and more water accumulates on the seed until a visible cloud is formed. In the case of ship tracks, the cloud seeds are stretched over a long narrow path where the wind has blown the ship’s exhaust, so the resulting clouds resemble long strings over the ocean.

Ship tracks provide an excellent way of studying the direct and indirect climatic impacts aerosols could have. 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.

Kármán Vortex Streets and Ship Tracks Off Coast of Baja California, Mexico

28.3N 118.5W

June 21st, 2011 Category: Clouds

Mexico - June 20th, 2011

Visible in the clouds off the coast of Baja California, Mexico, are two different phenomena: Kármán Vortex Streets (in the lower right quadrant of the thumbnail) and ship tracks (visible in the lower part of the full image).

Kármán Vortex Streets are double rows of swirled vortices that are caused by the unsteady separation of flow of a fluid over bluff bodies. Here, these bluff bodies are islands off the coast of Mexico.

In the full image, the dense white lines through the clouds at the bottom are ship tracks, clouds formed around the exhaust released by passing ships.


Ship Tracks off the Coast of Chile

38.8S 75.2W

October 21st, 2010 Category: Clouds

Argentina - October 12th, 2010

The two opaque white parallel lines of clouds cutting through the more through the translucent surrounding cloud cover are an atmospheric phenomenon known as ship tracks. Similar to airplane condensation trails, they form when water molecules gather around the exhaust released into the air by ships.

Parts of Chile and Argentina can be seen in the right half of the image. Although much of Chile is obscured by heavy cloud cover, some snow-capped ridges of the Andes Mountains can be observed, and the Argentine Patagonia terrain is cloud-free.

In related news about Chile, a 5.8-magnitude quake shook the central part of the country late on Wednesday, swaying buildings in the capital Santiago, but causing no damage, emergency officials said.

The quake’s epicenter was offshore in the Pacific Ocean 196 miles west-southwest of Santiago and at a depth of 4.2 miles (6.7), the U.S. Geological Survey said.

In February, Chile was struck by an 8.8-magnitude quake, one of the biggest in recorded history, killing more than 500 people and ravaging towns and industries in south-central Chile.