Scales of Atmospheric Motion

1. In the atmosphere, motion takes place at all spatial and temporal scales simultaneously.

2. Interaction between scales is always important and often mathematically complex.

3. Atmospheric energy cascades down scale from planetary scale ultimately to microscale where

energy is dissipated primarily through friction and re-radiation to space.

4. These “non-linear” down-scale interactions were expressed by L.F. Richardson

in the following verse:

"Great whirls have little whirls,

That feed on their velocity,

And little whirls have smaller whirls,

And so on to viscosity"

L.F. Richardson, (Circa 1922)

5. Do not think of energy as something magical. Think of energy as a property of

atmospheric gasses. Some molecules are dragged across the surface of Earth and

loose kinetic energy through friction others are transported high in the troposphere

and loose energy by re-radiation to space.

6. All that mass (the sum total of all the molecules moving through the energy cascade)

is recycled to once again take part in this graceful, never-ending ballet.

7. So in 1972 F. L. Gifford extended Richardson’s verse with:

"And the great whirls in turn supply

Still greater whirl's rotation;

And these feed greater still, up to

The General Circulation"

F.L. Gifford, (1972)

Horizontal Scale	Time (Life Span)	Distance	Example	Characteristic Energy Source
Planetary (Global)	Weeks to Seasons	4000 km to 40,000 km	Westerlies Trade winds Long waves	Unequal distribution of solar heating
Several	Sub-scales	Between	Planetary and Synoptic
Synoptic (Weather Map Scale)	Days to weeks	1000 km to 4000 km	Large Synoptic: Mid Latitude Cyclones Small Synoptic: Hurricanes	Jet Stream Latent heat of condensation
Several	Sub-scales	Between	Synoptic and Mesoscale
Mesoscale	Minutes to hours	1 km to 1000 km	Large Meso: Sea Breeze, Mountain Breeze Small Meso: Tornado Thunderstorm	Diurnal heating and cooling Latent heat Wind shear
Several	Sub-scales	Between	Mesoscale and Microscale
Microscale	Seconds to minutes	< 1 km	Large Micro: Dust devil Wind gust Small Micro: Building corner leaf-lifting eddy	Uneven surface heating Interaction with obstructions Air viscosity
Many	Possible divisions	Between	Microscale and Molecular scale
Molecular scale	Tiny fractions of a second	Billionths of a meter	Growth of raindrops Evaporation/condensation Wegner/Findeisen/Bergeron process UV -Ozone interaction Heat Transfer by conduction Blue sky	see the Kinetic Theory of gasses CLICK HERE