Describe the various scales of motion, and give an example of each.
Microscale- smallest scale of atmospheric motions.
For example small eddies with diameters
of only a few meters or less that not only disperse smoke they also sway branches, swirl dust
and papers into the air.
They form by convection or by the wind blowing past obstructions
and are usually short-lived, lasting only a few minutes at best.
Mesoscale – meaning “middle” scale whose circulations of winds range from a few
kilometers to about a hundred kilometers in diameter.
They last longer than microscale
motions, often many minutes, hours, or in some cases as long as a day.
circulations include local winds (which form along shorelines and mountains), thunderstorms,
tornadoes and small tropical storms.
Synoptic scale– or weather map scale whose circulations are around high and low pressure
Circulations of this magnitude dominate regions of hundreds to even thousands of
square kilometers and, although the life spans of these features vary, they typically last for
days and sometimes weeks.
It can cover an area ranging from the size of a continent to the
Planetary (global) scale - the largest wind patterns are seen at this scale.
These wind patterns
range over the entire earth.
Sometimes, the synoptic and global scales are combined and referred to as the macroscale.
How does the earth’s surface influence the flow of air above it?
The surface slows down air movement through friction. On a larger scale, this will also reduce
the Coriolis Force applied to the movement of the air.
What causes wind gusts?
Wind gusts are caused by a sudden increase in wind speed
How does mechanical turbulence differ from thermal turbulence?
Mechanical turbulence is are turbulent eddy motions caused by obstructions, such as trees,
buildings, mountains, and so on but thermal turbulence is a turbulent vertical motions that
result from surface heating and the subsequent rising and sinking of air.
Why are winds near the surface typically stronger and more gusty in the afternoon?
Thermal turbulence is associated with instability and convective activity. It is similar to
mechanical turbulence in its effects on surface winds, but extends higher in the atmosphere.
Since it is the result of surface heating, thermal turbulence increases with the intensity of
surface heating and the degree of instability indicated by the temperature lapse rate. It,
therefore, ages wind speed near the surface and decreases it aloft.
This is the reason surface
winds or gust are stronger in m ost places in the afternoon.
Describe several ways and Eddie might form.
When the wind encounters a solid object, a whirl of air, or eddie, forms on the object’s
Light winds produce stationary eddies.
Wind moving past trees, shrubs, and
even your body can produce small eddies.
Air flowing over buildings produce larger eddies,
Strong winds blowing past a stadium can produce eddies.
Wind blowing over a fairly smooth