In spite of the fact that a great deal of the enormous solar energy is broken or reflected when passing through the atmosphere the remaining penetrates it and gets to the surface of the Earth.Here,it is absorbed by the air,lands and/or ocean waters.the Earth and water , in turn, also send back a major portion of their received energy to the atmosphere.Since the rays emitted by the Sun are shone vertically to the Earth in equatorial regions,and on the contrary,the angle of shining is very small in areas around the poles , the amount of energy received in equatorial lands is much more than that of the polar ones : Therefore, some energy must be directed from the equatorial areas to the lands around the poles.Otherwise the weather in equatorial lands gets warmer day by day.This important phenomenon,that is the displacement of energy,is carried out through the displacement of air by convection currents which lead to the formation of wind. The displacement of air which,depending on the environmental and geogrophical conditiones,usually accompanies the formation and the displacement of clouds,is the main element for controlling a varieties of climates in different areas.A portion of these displacements,such as the usual movement of the air from equatorial regions towards the poles,generally affect the climatic coniditions on the Earth. The general movement of air begins from the equatorial regions.The hot and humid weather there ,in the form of an enormous mass ,is directed upwards and climbs to the upper layers of troposphere.While climbing up it loses its humidity in the form of clouds. The clouds produced after the cooling and climbing processes,cause heavy equatorial rainfalls after the equatorial warm air which lacks humidity moves upwards and gets to the heights,a portion of it turns toward the north and the other portion goes towards the south,and form the air currents above the atmosphere in these regions.A portion of this warm and dry air climbs and is directed toward the ground in latitudes of 30 to 40 degrees while eliminating the scant humidity existing in the areas through which it blows it causes an ever increasing dryness in the environment.That is why most of the dry regions in the world one located in the latitude between 30 to 40 degrees in the north and south latitudes )horse latitudes). Another example of the inter relation ships between air currents and clouds in determining the climate in an area , is the formation of clouds between the sea and the mountains over looking it : The wind which blows from the sea contains some water vapor. The movement of the wind towards the land and high places,which have lower air pressure than the sea,causes the damp air from the sea to move towards the foot of the mountain and makes an environment with move relative humidity.This air gets cooler as it goes up, at the same time its water vapor becomes dense;then it turns into clouds and rain and precipitates in the foot of the mountain over looking the see.The northern and southern faces of the Alborz mountain ranges in Iran and the effect of the moisture resulted from the Caspian sea and also changes in ecological conditions in the two feet of this mountain range are obvious examples of the facts mentioned. it must be noted that not all clouds are rain making.They act differently according to their formation mechanism,height,temperature and other environmental conditions.