NationMaster - Encyclopedia: Earth's atmosphere (Meteorology)

Earth's atmosphere (and its mechanics) can often be described in meteorology with very particular and specific terms. While meteorologists do use the more commonly understood standard terms for the earths atmospheric layers, these definitions are insufficient to describe most weather systems, as most weather tends to occur in the lower layers of the earth's atmosphere (most often the troposphere). Due to this deficiency, meteorologists have given further resolution to their observations by dividing this small and highly relevant section of the atmosphere into upper, middle, and lower levels. Each level has its own individual characteristics and properties, and is semi-independent of the others - while events and phenomena on a particular level can interact with features in the adjacent levels it is also possible for the atmosphere to flow in different directions at the same time (known as wind shear). Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... Layers of Atmosphere - not to scale (NOAA)[2] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Layers of Atmosphere - not to scale (NOAA)[2] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Atmosphere diagram showing the mesosphere and other layers. ... The word resolution has several meanings, depending on context. ... Wind shear is a difference in wind speed or direction between two points in the atmosphere. ...

The motion of wind, atmospheric/meterorological phenomena and events is also described in specific terms, most usually being "zonal" and "meridonial" flow. Whilst the earths atmosphere flows in general direction of west to east at the lower tropospheric layer, anomalies frequently arise, and so these terms are used to describe the difference between a flow that follows the general trend and a flow which is diverted from that trend.

On a synoptic scale (which can be thought of as the size/area and timespan of individual significant atmospheric events such as depressions or anticyclones rather than a global scale), observations of the motions, trends, and themes of yet smaller sections of the earths atmosphere are also often described in specialist terms. It has been suggested that this article or section be merged into Synoptic scale meteorology. ... In meteorology, an anticyclone (i. ...

Atmospheric levels

There are three "levels" often used by meteorologists to describe the height and vertical range of an atmospheric event or phenomenon. Each level is roughly defined, and so there can only be approximate definitions of each.

Low level

The lower level of the atmosphere is that which is at the surface (around sea level and upwards towards 6,000 to 8,000 feet above sea level. ^[1]

Mid level

The mid level lies between the lower and upper levels, corresponding to around roughly 6,000 - 25,000 feet.^[2]

Upper level

This is the highest of the three levels. The term applies to the portion of the atmosphere that is above the lower troposphere, generally 850 hPa and above.^[3]

Atmospheric flow

The flow of the atmosphere generally moves in a west to east direction. This however can often become interrupted, creating a more north to south or south to north flow. These scenarios are often described in meteorology by as zonal or meridonial. These terms, however, tend to be used in reference to localised areas of atmosphere (at a synoptic scale)). A fuller explanation of the flow of atmosphere around the Earth as a whole can be found in the three-cell model. It has been suggested that this article or section be merged into Synoptic scale meteorology. ... Earths atmosphere (and its mechanics) can often be described in meteorology with very particular and specific terms. ...

Zonal Flow

A zonal flow regime is the meteorological term meaning that the general flow pattern is west to east along the earth's latitude lines, with weak shortwaves embedded in the flow.^[4] The use of the word "zone" refers to the flow being allong the Earths lattitudinal "zones". This pattern can buckle and thus become a meridonial flow. Zonal flow is a meteorological term meaning that the general flow pattern is west to east along the earths latitude lines (as opposed to meridional flow). ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ...

Meridonial flow

When the zonal flow buckles, the atmosphere can flow in a more longitudinal (or meridonial) direction, and thus the tem "meridonial flow" arises. Meridional flow patterns feature strong, amplified troughs and ridges, with more north-south flow in the general pattern than west-to-east flow. ^[5] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

Three-cell model

The three cell model attempts to describe the actual flow of the earths atmosphere as a whole. It is comprised of the tropical (Hadley cell), mid latititude (Ferrel cell), and polar (polar cell) regions of the earth, dealing with energy flow and global circulation. Its fundamental principle is that of balance - the energy that the earth absorbs from the sun each year is equal to that which it loses back into space, but this however is not a balance precicely maintained in each latitude due to the varying strength of the sun in each "cell" resulting from the tilt of the earths axis in relation to its orbit. It demonstrates that a pattern emerges to mirror that of the ocean - the tropics do not continue to get warmer because the atmosphere transports warm air poleward and cold air equatorward, the purpose of which appears to be that of heat and moisture distribution around the planet.^[6] Atmospheric circulation is the large-scale movement of air, and the means (together with the ocean circulation, which is smaller [1]) by which heat is distributed on the surface of the Earth. ... The Hadley cell is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10-15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface. ... The Ferrel cell is usually shown between the Hadley and Polar cells, e. ... The polar vortex is a persistent, large-scale cyclone located near the Earths poles, in the middle and upper troposphere and the stratosphere. ...

Synoptic scale observations and concepts

Forcing

Forcing is a term used by meteorologists to describe the situation where a change or an event in one part of the atmosphere causes a strengthening change in another part of the atmosphere. It is usually used to describe connections between upper, middle or lower levels (such as upper-level divergence causing lower level convergence in cyclone formation), but can sometimes also be used to describe such connections over distance rather than height alone. In some respects, tele-connections could be considered a type of forcing.

Shortwave and Longwave

Divergence and Convergence

Atmospheric convection

Contents

Atmospheric levels

Low level

Mid level

Upper level

Atmospheric flow

Zonal Flow

Meridonial flow

Three-cell model

Synoptic scale observations and concepts

Forcing

Shortwave and Longwave

Divergence and Convergence

Atmospheric convection

See also

References

External links

Contents

Atmospheric levels GA_googleFillSlot("encyclopedia_square");

Low level

Mid level

Upper level

Atmospheric flow

Zonal Flow

Meridonial flow

Three-cell model

Synoptic scale observations and concepts

Forcing

Shortwave and Longwave

Divergence and Convergence

Atmospheric convection

See also

References

External links

Atmospheric levels