Atmosphere — Geography STD 11 Arts — Question

The average conditions of weather over a longer period of time is Climate.

Normally climate is determined on the basis of weather conditions of a region over a period of $35$ years or more.

Elements of Climate:

$(1)$ Insolation and Temperature:

 

The heat received from the Sun is known as Insolation.

Amount of insolation varies with latitude.

In tropical regions, Sun rays fall vertically, so temperature remains high.

In Polar Regions.

Sun’s rays fall oblique, so temperature remains low.

On the basis of insolation and temperature, a regions climate may be hot or cold, moderate or extreme.

$(2)$ Pressure and Winds:

 

Latitude, distance from the sea, physical features, location, altitude, forest regions and such other factors result in formation of low and high pressure areas.

Low pressure is experienced in equatorial regions due to heat, while in cold Polar Regions; high pressure is experienced due to the cold.

Thus, under the influence of various factors, low and high pressures are formed.

Air moves from areas of high pressure to that of low pressure.

When there is high pressure over the sea, moist winds from here blow towards the low pressure areas over continents and bring rain.

As winds coming from sea are cool, sea coast has a moderate climate.

In areas where dry winds blow, there is scanty rain and climate becomes extreme.

Thus, pressure and winds play an important role in changing climate of a region.

$(3)$ Humidity and Rain:

 

Water present in the atmosphere in the form of vapour is Humidity.

Amount of humidity depends on the rate of evaporation.

In dry desert regions due to less rain and in polar regions due to less evaporation, humidity is low.

Hence there is low rainfall. In equatorial regions, Sun’s rays fall vertically throughout the year and so there is highest evaporation.

Worlds heaviest rainfall is recorded here.

Air moisture makes the weather steamy.

Hence the humid climate of equatorial region is not healthy for humans.

Thus humidity and rain determine whether climate is dry or humid.