Rossby Waves, Hadley Cells and the Jetstream

Rossby Waves, Hadley Cells and Distorted Jet Stream

Seems that Global Warming has a lot to do with the difficulties we are experiencing with our weather. The Jet Stream is pretty neat without Global Warming and very predictable and so is the weather. Recently, the northern hemisphere experienced massive cool events and extremely cold weather. Why?

So what does the Jet Stream do normally?

The circulating air patterns create convection currents in four global locations—each current is called a Hadley cell. The pattern of air movement is toward the Earth (pro-grade) at higher latitudes (in the subtropics) and backward (up from the Earth) at lower latitudes (near the equator). The movement occurs near the Earth’s surface—within 6.2-9.3 mi. (10-15 km.). Its span across latitudinal markers remains within thirty degrees north or south of the equator. In this way, a Hadley cell moves heat from the equatorial region to regions within 30 degrees of latitude in either direction. Moisture is moved along with the heat.

Hadley Cells

Hadley Circulation provides westward wind flow at the Earth’s surface (Trade Winds) and eastward jet streams at higher altitudes. The circulating air patterns create convection currents in four global locations—each current is called a Hadley cell.

HadleyCirculation

In a Hadley cell, the air rises to the atmospheric tropopause, which is the region at the top border of the troposphere and thus the bottom border of the stratosphere. The troposphere is the lowest atmospheric region and is where all weather takes place. At the equator, it reaches up to 11 mi. (18 km.) from the earth’s surface.

The next atmospheric layer is the stratosphere, extending to 31 mi. (50 km.) from the Earth’s surface. This characteristic air circulation results from the Sun’s rays heating the air at the level of the equator. Solar heating is strongest at the equator and weakest at the north and south poles, due to the direction of the Sun’s rays, and therefore currents of atmospheric circulation due to solar heating are more prominent at the equator.

Hadley Circulation was first described by George Hadley (1685-1768) to explain the science behind the trade winds. It was to replace a flawed model that had been presented by Edmond Halley (1656-1742). George Hadley was an early 18th century meteorologist by hobby and lawyer by trade.

In fact, Hadley’s theory was imperfect as well. It was corrected by American meteorologist William Ferrel (1817-91) at the end of the 19th century, but by this time Hadley’s name had stuck. The Hadley Circulation is traditionally defined as resting on the equator; in fact it rests on the “thermal equator,” or the Sun’s zenith.

Rossby Waves

Rossby Waves - Jet sStreamWarming Arctic May Be Causing Jet Stream To Lose Its Way. Echoing trends since roughly 2010-2011, NPR reports on how changes in far northern latitudes may be showing up in the skies floating above your house; here’s an excerpt: “…The temperature difference between the Arctic and lower latitudes is one of the main sources of fuel for the jet stream; it’s what drives the winds. And because the Arctic is warming so fast, that temperature difference is getting smaller, and so the fuel for the jet stream is getting weaker,” Francis says. “When it gets into this pattern, those big waves tend to stay in the same place for some time. The pattern we’ve seen in December and January has been one of these very wavy patterns...”

Image credit above: “The jet stream that circles Earth’s north pole travels west to east. But when the jet stream interacts with a Rossby wave, as shown here, the winds can wander far north and south, bringing frigid air to normally mild southern states.” NASA/GSFC.