Wind and Deserts



Pressure

The weight of the air above an object exerts a force upon that 
object, and this force is called pressure. 
Variations in pressure lead to the development of winds that 
play a significant role in shaping our daily weather.
Winds flow from areas of high pressure to areas of low 
pressure - clockwise in the northern hemisphere


Clouds


A visible aggregate of tiny water (or ice) droplets suspended 
in the air
Relative Humidity - 75% relative humidity means that the air 
contains three-quarters the amount of water vapor required for 
saturation.

Dew point temperature is defined as the temperature to which 
the air would have to cool (at constant pressure and constant 
water vapor content) in order to reach saturation.

As air rises it tends to cool and water vapor may condense if 
saturation is reached

Convective - hot air rises
Convergence - two air masses meet and air column is forced 
upwards
Orographic





Interactions in the Atmosphere


Reflection



Scattering - Oxygen and Nitrogen scatter the shorter 
wavelengths - sky is blue


Refraction





Diffraction - light bends around an object





If incoming solar radiation is 100 units:


	16 units are absorbed by dust, water and ozone;
	  3 units are absorbed by clouds;
     6 units are scattered back by air;
   20 units are reflected by clouds;
     4 units are reflected by the surface.


30 reflected back to atmosphere - the albedo - reflectivity : if 
the albedo decreased, the temperature goes up
Earth receives 51 units





These units heat up the Earth's surface and infrared radiation 
is emitted.  The Earth's atmosphere absorbs some of this 
radiation.
The greater the amount of absorbers (such as carbon dioxide), 
the greater the amount of heat absorbed and the higher the 
temperature.


Thus, the Earth's atmosphere is relatively transparent to 
visible light but absorbs some of the outgoing infrared.
Ozone (O3) absorbs ultraviolet - high energy


Aeolian Sedimentation	


Modification of grain shape by the wind
Accumulations
Dune Fields
Erosional Features
The Rock Record