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Archive for Clouds

Dust and Kármán Vortices by Canary Islands – June 23rd, 2013

21.0N 19.1W

June 23rd, 2013 Category: Clouds, Dust Storms, Image of the day VIIRSSuomi-NPP

West Africa – June 22nd, 2013

Named after the engineer and fluid dynamicist Theodore von Kármán, in fluid dynamics, a Kármán vortex street is a repeating pattern of swirling vortices that are created when the flow of a fluid separates unsteadily as it moves around blunt bodies. Here, this phenomenon can be seen in the upper left quadrant, as spiralled cloud patterns southwest of the Canary Islands. In the lower left quadrant, dust can be seen blowing off the coasts of Mauritania and Senegal.

Kármán Vortex Streets Trailing Off Cape Verde and Canary Islands – June 20th, 2013

21.8N 18.5W

June 20th, 2013 Category: Clouds, Image of the day VIIRSSuomi-NPP

West Africa – June 19th, 2013

West of Western Sahara, Mauritania and Senegal, off the coast of West Africa, is an atmospheric phenomenon known as Kármán Vortex Streets. These parallel rows of oppositely spinning vortices, caused by the unsteady separation of flow of a fluid around blunt bodies, can be seen trailing off the Canary Islands (above) and off the Cape Verde islands (below). Some dust can also be seen spreading off the coast of Mauritania.

Haze Over Eastern China

39.0N 116.4E

June 12th, 2013 Category: Clouds MODISAqua

China – June 12th, 2013

Here, haze can be seen over the eastern part of China, near the Bohai Sea. China is the world’s largest emitter of carbon dioxide (pumping out some 10 gigatons of carbon dioxide in 2011), and has vowed to reduce such emissions per unit of gross domestic product by 40 to 45 percent of the country’s 2005 levels by 2020.

However, scientists have suggested that current efforts to cut harmful greenhouse gases fall short because of the way they set targets for the highest polluting areas. China’s lesser-developed heartland is actually responsible for 80 percent of carbon dioxide emissions related to goods consumed along the wealthier coast.

Spiralled Area of Convection East of Japan

39.5N 147.8E

June 10th, 2013 Category: Clouds VIIRSSuomi-NPP

Tropical Storm Yagi (03W) – June 9th, 2013

While Tropical Storm Yagi (03W) churns to the south of Japan, a large, spiralling area of convection can also be observed to the east of the country. Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world.

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).