Presentation on weather and climate simi

It is often confused with the term ‘climate” Weather is the state of temperature, pressure, winds, humidity, precipitation etc. at a given place and time. It is often confused with the term ‘climate” r A

Factors affecting weather and climate Atmospheric temperature Atmospheric pressure Wind Moisture Cdc

1. ATMOSPHERIC TEMPERATURE

Atmospheric Temperature The main source of heat on the earth is the Sun. The heat and light received by the Sun is called Solar radiation. A very small amount of solar radiation reaches the earth surface. This is called Insolation. Its distribution

The earth absorbs maximum solar radiation during the day. At night, it is radiated back to the atmosphere. This is called terrestrial radiation.

Heating of the atmosphere The air over the earth surface gets heated due to its contact with the surface. It becomes lighter and rises up. Thus, different layers of atmosphere are heated.

Distribution of Temperature on the earth The amount of insolation received on the earth surface is not the same. It goes on decreasing from the equator to the poles. The earth is thus, divided into three heat zones.

Heat zones of the Earth

Measurement of atmospheric temperature The instrument to measure temperature is called thermometer. It has two scales- 1. Fahrenheit (melting point of ice is 32 degree and boiling point of water is 212 degree) 2. Celsius (melting point of ice is 0 degree boiling point is 100 degree)

2. ATMOSPHERIC PRESSURE

Atmospheric Pressure The atmosphere exerts its weight as pressure on the earth’s surface. This is called Atmospheric Pressure. The weight of air column is maximum at the mean sea level. I

Measurement of Atmospheric Pressure It is measured with an instrument called Barometer. The normal atmospheric pressure at sea level is 76 cm of the mercury column in the barometer. Millibar(mb) is the unit to measure atmospheric pressure.

Barometers

Distribution of Atmospheric pressure on the Earth surface It decreases with increase in altitude. It decreases with increase in moisture in air. Earth’s rotation changes the Atmospheric pressure. It decreases with increase in temperature.

There are seven major pressure belts on the Earth surface 1. Equatorial low pressure belt 2. Northern Sub Tropical high pressure belt 3. Northern Sub Polar low pressure belt 4. Northern Polar High pressure belt. 5. Southern Sub Tropical high pressure belt. 6. Southern Sub Polar low pressure belt. 7. Southern Polar high pressure belt.

Major Pressure Belts

3.WINDS

Winds Horizontal moving air is called wind. It moves from a high pressure region to a low pressure region. It is named after the direction from where it blows.

Ferrel’s Law or Coriollis Force states that due to Earth’ s rotation the wind is deflected towards the right in the Northern Hemisphere the left in the Southern Hemisphere

Measurement of wind speed &direction The speed of the wind is measured by an Anemometre. The direction of wind is found by a Wind Vane

Types of Winds Planetary winds Periodic winds Local winds Also called as permanent winds Mainly originate due to presence of permanent pressure belts. Examples –Trade winds,Westerlies and Polar winds Planetary winds These blow in definite direction during a particular time of the day or year Mainly originate due to differential heating of the earth surface or local difference of atmospheric pressure. Examples-Monsoon winds, Land and Sea breeze. Periodic winds These blow over a small area and for a short Period Mainly derive local names. Examples-Loo, Chinook,Harmattan. Local winds

4.MOISTURE

Moisture Amount of water present in atmosphere is called Moisture. It is present in all three forms i.e. solid, liquid and gaseous

Moisture- some facts Moisture in air varies from place to place. There is more moisture in air in the summer season. The amount of moisture decreases with height above the sea level. The amount of moisture in the air is about zero at the poles in winters. The air in equatorial regions has maximum moisture.

Water (Moisture)Cycle Evaporation Condensation Precipitation

Evaporation Rising of water from the earth to the atmosphere in form of water vapour is called Evaporation. It takes place at all times at all places. It increases on a hot and windy day.

Condensation When the air rises up in the atmosphere, it becomes cool and water vapour changes into tiny droplets. This is called Condensation. It takes place around dust particles in the air.

Condensation Forms of condensation Clouds Dew Fog

Clouds are water drops condensed around dust particles Cirrus Cumulus Stratus

Precipitation When clouds get saturated with water vapour they fall on earth. This is called Precipitation.

Types of Precipitation Rain Drizzle Snow Hailstones

Types of Rainfall