Atmospheric turbulence

other. Laminar motion.

Speed of the ink particle are faster than the speed of general motion. The ink jet starts meandering.

Fast motion. Trajectories of the motion distorted. That is turbulent motion.

Small vortexes produced by the turbulence are known as EDDIES.

Water-pipe tap is opened just slightly A small water jet is smooth (laminar motion).
Water pipe tap is opened widely The water jet is rough (Turbulent or eddy motion)

flow, a Reynolds number above about 4000 will most likely correspond to turbulent flow,
while a Reynold's number below 2100 indicates laminar flow.
The region in between (2100 < Re < 4000) is called the transition region.

Laminar and turbulent flow of cigarette smoke

character of liquid (gas) motion is suggested by Reynolds Number.

Density of the liquid (gas)

Dynamic coefficient of molecular viscosity

Speed of motion

Distinctive (typical) scale of motion

In case ρ and η are constant (that is true for a certain medium), the number Re depends on the speed and distinctive scale of motion.

Critical value of the number Re is different for different substances and conditions. As the number of Re reaches its critical value, the motion is transferred into turbulent character.

Calculation Re numbers for the atmosphere suggested that the motion in the atmosphere are always turbulent.

Along with Re number there are some others criteria for character of motion and intensity of the eddy development.

rapid fluctuation of meteorological parameters. However, along with chaotic motion, all air particles are subjects to move with a mean speed. Therefore, momentary speed of motion c* can be presented as:

or

Mean speed

Pulsation

Notion of admixture specific content

A unit of air mass

Mass of water vapor

Mass of ozone

Mass of CO2

Mass of solid and liquid aerosols

Mass of a substance in a unit or air mass is called ADMIXTURE SPECIFIC CONTENT (ASC)

For instance, the water vapor content is known as specific humidity (s), or fraction of water vapor.

ASC vary in a wide range both in horizontal and vertical directions

part in eddy mixing is called
EDDY (TURBULENT) MOLE.

Mean flow

Mixing length

The heaven is infinity in time and space!

Any man is an insignificant particle in this infinity and boundlessness. What is the symbol of the infinity and boundlessness on the Earth? Certainly, it is the heaven! Any one appears from the infinity and goes into the infinity after his life is over, like an eddy mole, being formed in an atmospheric current, after a while mixes into the current and disappears there forever! (prof. G.G.Tarakanov)

some physical properties of the air such as heat, moisture, and momentum. The most remarkable mixing takes place in vertical direction.
Usually ASC decreases with height (∆s<0), but in some rare cases, it can be opposite (∆s>0). Eddy mixing results in equalization of ASC.

Z+∆Z

Z

Zi

s+∆s

s

The mass of admixture transferred by the eddy mixing for a unit of time through a unit of the surface at the altitude Zi is called FLUX OF ADMIXTURE (Q).

It is obvious that the eddy flux must be proportional to the difference of ASC at the level Z and ∆Z related to a unit of the distance between those levels, i. e.

Coefficient of eddy exchange (mixing coefficient)

value depend on: wind velocity and its variation, static stability, properties of the underlying surface, etc

Postulate of eddy exchange

During an interval of time, the amount of transferred substances through a surface upward and downward must be equal.

Wind pulsation

Mixing length, L

A and K values

coefficient increases with height is called SURFACE LAYER

20 m

The most frequently S. L. height is 50 – 100 m

K values vary from to

There are also molecular fluxes of various substances

D is molecular diffusion coefficient

We may neglect molecular fluxes

0 (few km)
Surface layer – k increases (decimals –hundreds of m)
Subsurface layer – laminar motion ( close to Earth surface, 2 mm)

fluid where the scale of turbulent eddy is limited by the eddies' proximity to an interface. The objects highlighted in white above are turbulent eddies whose size is constrained by the proximity of the center of each eddy to the surface.

The surface layer is the layer in a fluid where the scale of turbulent eddy is limited by the eddies' proximity to an interface. The objects highlighted in white above are turbulent eddies whose size is constrained by the proximity of the center of each eddy to the surface.

http://en.wikipedia.org/wiki/Surface_layer

be neglected