Date: March 01, 2015
Roaring Forties Earth’s rotation Screaming Sixties Furious Fifties
Q- What do you understand by ‘ROARING FORTIES’? Explain the mechanism of formation of roaring fourties? [200 WORDS]
The Roaring Forties are strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 50 degrees.The strong west-to-east air currents are caused by the combination of air being displaced from the Equator towards the South Pole and the Earth’s rotation, and there are few landmasses to serve as windbreaks. The Roaring Forties refers to the belt of ripping westerly winds, aided by the Earth’s rotation, between roughly 40 and 50 degrees latitude in the southern hemisphere. Winds rage in this region as it sits in the transition zone between the more tranquil, balmy subtropics and frigid polar vortex zipping around the South Pole. Pressures and temperatures change rapidly here, driving the winds frequently over 30-40 mph, and give rise to storms.
The winds in the Roaring Forties belt are some of the fastest in the world, but topped at times by adjacent latitude zones to the south known as the Furious Fifties and Screaming Sixties.The boundaries of the Roaring Forties are not consistent, and shift north or south depending on the season. Similar but stronger conditions occur in more southerly latitudes and are referred to as the Furious Fifties and Shrieking or Screaming Sixties.
Mechanism of Roaring forties
Hot air rises at the Equator and is pushed towards the poles by cooler air travelling towards the Equator (an atmospheric circulation feature known as the Hadley Cell). At about 30 degrees from the equator, the outward-travelling air sinks to lower altitudes, and continues toward the poles closer to the ground (the Ferrel Cell), then rises up again from about 60 degrees as the air joins the Polar vortex. This travel in the 30 to 60 degree zone combines with the rotation of the earth to move the air currents from west to east, creating westerly winds
Unlike the northern hemisphere, the large tracts of open ocean below 40th parallel south (interrupted only by Tasmania, New Zealand, and the southern part of South America) mean that higher windspeeds—the Roaring Forties—can develop. Similar but stronger wind conditions are prevalent closer to the South Pole; these are referred to as the “Furious Fifties” (50 to 60 degrees south), and the “Shrieking” or “Screaming Sixties” (below 60 degrees south). The latitude ranges for the Roaring Forties and similar winds are not consistent, shifting towards the South Pole in the southern summer, and towards the Equator in the southern winter.