Precipitation
Falling down of condensed water vapour in different forms is called Precipitation. When the dew point is reached in the cloud water droplets become saturated and start to fall. Hence, they fall on the earth as precipitation.
The climatic conditions/ factors influencing the forms of precipitation mainly are:
• Temperature.
• Altitude.
• Cloud type.
• Atmospheric conditions.
• Precipitation process.
The main forms of precipitation include drizzle, rain, sleet, snow, hail, etc.
Drizzle: Falling of numerous uniform minute droplets of water with diameter of less than 0.5 is called a drizzle.mm from low clouds. Sometimes drizzles are combined with fog and hence reduce visibility.
Rain: Rain is the most widespread and important form of precipitation in places having temperature above the freezing point. It occurs only when there is abundant moisture in the air. The diameter of a rain drop is more than 5 mm.
Sleet: Sleet refers to a precipitation, in the form of pellets made up of transparent and translucent ice. This precipitation is a mixture of snow and ram.
Snow: Snow is formed when condensation occurs below freezing point. It is the precipitation of opaque and semi opaque ice crystals. When these ice crystals collide and stick together, it becomes snowflakes.
Hails: Hails are chunks of ice (greater than 2 em in diameter) falling from the sky, during a rainstorm or thunderstorm. Hailstones are a form of solid precipitation where small pieces of ice fall downwards. These are destructive and dreaded forms of solid precipitation because they destroy agricultural crops and human lives.

The term cyclone is a Greek word meaning "coil of a snake". Cyclones are centres of low pressure where, winds from the surrounding high pressure area converge towards the centre in a spiral form. Due to the rotation of the earth, the cyclonic winds in the northern hemisphere move in anti clock wise direction, where as they move in clockwise direction in the southern hemisphere.
Cyclones can be classified into Tropical cyclones, Temperate cyclones and Extra tropical cyclones.
Tropical cyclones: Tropical cyclones develop in the Inter tropical convergence zone [ITCZ]. They are formed due to the differential heating of land and sea. Tropical cyclones are known as 'cyclones' in Indian ocean, 'typhoons' in the western pacific ocean, 'hurricanes' in the Atlantic and eastern Pacific ocean, 'baguios' in Phillipines and 'willy willy' in Australia. Tropical cyclones often cause heavy loss of life and property on the coasts and become weak after reaching the landmasses.
Temperate cyclones: Temperate cyclones are formed along a front where hot and cold air masses meet in mid-latitudes between 35° and 65°N and S. Temperate cyclones do not become weak like the tropical cyclones on reaching the land. Temperate cyclone commonly occurs over the North Atlantic Ocean, North West Europe, Mediterranean basin. Mediterranean basin's temperate cyclones extend up to Russia and India in winter. In India it is as called western disturbances.
Extra tropical cyclones: Extra tropical cyclones occur in the latitudes between 30° and 60° in both the hemispheres. They are also called as mid-latitude cyclones. They collect energy from temperature differences which are found in higher latitudes. Extra tropical cyclones produce mild showers to heavy gales, thunderstorms, blizzards, and tornadoes.

According to their height, clouds are classified into the following types
(i) High clouds (6 - 20 km Height)
(ii) Middle clouds (2.5 km - 6 km Height)
(iii) Low clouds (ground surface to 25 km height)
These major types of clouds are further divided into different types on the basis of shape and structure.
High clouds
Cirrus: Detached clouds in the form of white delicate fibrous silky filaments formed at the high sky (8000 meters to 12000 meters) are called Cirrus clouds. These clouds are dry and do not give rainfall.
Cirro-cumulus: White patched, sheet or layer like clouds composed of ice crystals.
Cirro-stratus: Smooth milky transparent whitish clouds composed of tiny ice crystals,
Middle clouds
Alto-stratus: Thin sheets of grey or blue coloured clouds in uniform appearance, consisting of frozen water droplets.
Alto-cumulus: clouds fitted closely together in parallel bands, called as 'Sheep clouds' or wool pack clouds.
Nimbo stratus: These are clouds of dark colour very close to the ground surface associated with rain, snow or sleet.
Low clouds
Strato-cumulus: Grey or whitish layer of non-fibrous low clouds found in rounded patches at a height of 2500 to 3000 metres, associated with fair or clear weather.
Stratus: Dense, low lying fog-like clouds associated with rain or snow.
Cumulus: Dome-shaped with a flat base often resembling a cauliflower, associated with fair weather.
Cumulo-nimbus: Fluffy thick towering thunderstorm cloud capable of producing heavy rain, snow, hailstorm or tornadoes.

WIND
(i) The horizontal movement of air along the surface of the earth is called the 'wind'.
(ii) The vertical movement of air is called an 'Air current',
(iii) The winds always blow from a high pressure area to a low pressure area.
PLANETARY WINDS
(i) The winds which constantly blow in the same direction throught the year are called the planetary winds.
(ii) These winds are Trade winds, Westerlies and Polar Easterlies.
TRADE WINDS
(i) Trade winds blow from the sub-trophical high pressure belt to the Equatorial low pressure belt in both the hemisphere.
(ii) They blow in a constant direction throughout the year.
(iii) These winds were very helpful to traders who depended on the winds while sailing in the seas.
WESTERLIES
(i) Westerlies are the permanent wind that blow from the tropical high plressure belt to the sub polar low pressure belt in both the hemispheres.
(ii) The velocity of Westerlies become vigorous.
(iii) It is called Roaring forties at 40^o, Furious fifties at 50^o and Screaming sixties at 60^o latitudes.
POLAR EASTERLIES:
(i) Polar easterlies are cold and dry polar winds that blow from the high pressure belt to the sub polar low pressure belt.

Atmosphere:
The blanket of air that surrounds the Earth is called the atmosphere. The five atmospheric layers are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
Troposphere: The lowest layer of the atmosphere is the troposphere. The Greek word 'tropos' means 'turn' or change. The layer extends up to 8 kms at the poles and up to 18 kms at the Equator. The temperature decreases with increasing height. Almost all weather phenomenon take place in this layer. Hence it is called weather making layer. The upper limit of the troposphere is called as tropopause.
Stratosphere: Stratosphere lies above the troposphere. It extends to a height of about 50 km above earth surface. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere.The temperature increases with increase in height in this layer, Large jet planes normally fly here. The upper limit of the stratosphere is called as stratopause.
Mesosphere: Mesosphere extends between 50km and 80km. The temperature increases with increasing height. Radio waves transmitted from earth are reflected back to earth from this layer: Most of the meteors nearing the earth, get burned here. The upper most limit of the mesosphere is the mesopause.
Thermosphere: Thermosphere exists above the mesosphere. It extends to about 600 km. The composition of gases in the lower thermosphere is more or less uniform, hence it is called "Homosphere". The upper portion of the thermosphere has uneven composition of gases and hence it is referred as "Heterosphere". Here the temperature increases with increasing height.Ionosphere is a layer of the thermosphere that contains Ions. and free electrons.
Exosphere: The uppermost layer of the atmosphere is called exosphere. This layer is extremely rarefied with gases and gradually merges with the outer space. This zone is characterized by aurora Australis and aurora borealis