The Origins of Everything in 100 Pages (More or Less) by David Bercovici

Author:David Bercovici
Language: eng
Format: epub
Publisher: Yale University Press
Published: 2016-04-08T04:00:00+00:00

Atmospheric convection acts to transport hot air from the tropics to the poles, and cold air in the reverse direction. Rotation of the Earth, however, breaks the convective circulation into three counter-rotating cells in both the Northern and Southern hemispheres. Air flowing at the bottom of each cell is deflected east or west because of Earth’s rotation (and depending on whether the air is flowing toward or away from the equator), and these currents comprise the prevailing winds in the Earth’s atmosphere. (Courtesy Barbara Schoeberl, Animated Earth LLC.)

Atmospheric convection cells also determine how water is transported across the planet through the atmosphere. The intense heating at the equator also evaporates a lot of water and this is carried in the warm upwellings. As these upwellings travel to higher altitudes and then spread horizontally north and south, the air cools and the water condenses, creating clouds and rain (hence why the tropics are so humid and rainy). By the time this air reaches its downwelling points at plus or minus 30 degrees latitude, it has lost its water, and so when it descends it is very dry and thus tends to dry out the ground on which it lands; this leads to aridified zones like the Sonoran and Sahara deserts and much of inland Australia as well as Mediterranean environments where arid land meets the sea, such as in (of course) the Mediterranean and much of California. These zones of different climate and humidity played important roles in the development of agriculture and thus the tides of human history and prehistory.

Much of Earth’s atmospheric (and thus ocean) circulation is governed by our planet’s relatively rapid spinning motion, as described above. Venus has very little spin and even revolves slowly backward (that is, opposite to Earth’s spin and that of most other planets in our system) every 243 days, which is even slightly longer than a Venusian year (about 225 Earth days long). Why Venus has such a slow and odd rotation is one of many mysteries about our sister planet. Despite its sluggish spin, Venus has strong winds, which, in its near-equatorial upper atmosphere, flow opposite the direction of planetary rotation (on Earth, the top of the Hadley cell flows in the same direction of rotation). Mars’s spin is almost exactly the same as Earth’s (for no apparent reason, just chance probably), and even with its very thin, mostly carbon dioxide atmosphere, Mars has something close to a Hadley circulation transporting heat and even water vapor from the equator toward the poles; this circulation also excites vigorous winds that can drive massive dust storms that sometimes engulf the planet for months at a time.

Although I’m being Earth-centric and giving only sparse comparison to our nearby terrestrial planets, it would be too provincial not to mention the fascinating atmospheres of Jupiter and Saturn. Both planets have pretty much the same composition of the pre-solar nebula, which was still basically the same as the Universe after the Big Bang, with some modification. This

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.