Sun : The Ultimate Source

Latitude refers to the distance between the locations on the earth from the equator. The land nearer to the latitude receives more sunlight as compare the land away from the equator. This is the reason the sunlight is extreme in the location nearer to the equator. Tropical regions experience more sunlight because rays of the sun are vertical thus receives more energy. On reaching close to the poles the angle of incidence of the sun's rays becomes more slanting. Due to this, there is a loss of energy because the sun has to travel through the atmosphere more.

NOTE – Tropical regions refers to the area nearer to the equator.

Temperature is higher over the land as compared to the sea during the summer time. The situation becomes the opposite during the winter time. So, the isotherms bend based on the difference in heating of land and water.

Relative humidity is defined as the ratio between the amount of water vapour and the total water holding capacity of the atmosphere. It is measured with the instrument called wet and dry bulb thermometer. If the relative humidity is 100%, it means that the absolute humidity is equal to the total water holding capacity at a particular temperature. Absolute humidity is the definite amount of water present in the atmosphere. So, when the atmosphere is fully saturated than condensation begins which results in the form of Frost, Mist/Fog, Dew and clouds.

Constant condensation results in the droplets present in the clouds to grow bigger in size. Due to this water droplets releases from the clouds and fall on the earth when it is not able to withstand the gravitational force of the earth.

(a)

(c)

The wind filled with moisture from the sea enters into the land. Gradually, it moves upwards through the mountain slopes and cools down there. After condensing it led to the formation of clouds.

The windward side as shown in the figure receives heavy rainfall whereas the other side or the leeward side does not receive rainfall. It is because on the leeward side the dry air is descending. The leeward side which does not receive rainfall is also known as rain shadow regions. This type of rainfall is known as orographic rainfall or relief rainfall.

The term heat budget refers to the balance between insolation and terrestrial radiation.

Shown below is the heat budget – consider that total amount of insolation = 100 units. It is reaching on the outer surface of the atmosphere. Now let us see how these 100 units of energy are distributed.

In the weather station, various instruments are used such as Maximum-minimum thermometer, Wet and dry bulb thermometer, Barometer, anemometer, etc. The various functions of the weather instruments are as follows:

• Weather instruments are used to measure maximum and minimum temperature per day and also overall atmospheric temperature.

• The relative humidity is calculated.

• To measure air and sea surface temperature.

• To measure atmospheric pressure.

• To measure wind speed and direction.

• To measure the amount of rainfall.

When condensation of water vapour happens around the dust particles present in the atmosphere, clouds are formed. Water droplets which formed are less than 0.001 cm in dimension. Clouds are classified based on their height and form which are as follows:

• Cirrus clouds – this type of clouds is present in the upper atmosphere when the weather is clear. These are the feather-like clouds.

• Stratus Clouds – this type of clouds is present in the lower part of the sky which is in a thick layer.

• Cumulus clouds – this type of clouds looks like the huge cotton bundles. These are formed by the strong convection currents and have large vertical coverage.

• Nimbus clouds – this type of clouds appear as dark rain clouds present in the lower atmosphere. Nimbus clouds didn’t allow sunlight to pass through them as the concentration of water droplets is thick.

Clouds appear in different forms at the same time, for example - cumulus and nimbus clouds appear together is termed as cumulo-nimbus clouds.

QUIZ COMPETITION

Ques. Name the term used to refer to the degree of hotness of the atmosphere.

Ans: Temperature.

Ques. Heat budget is the balance between

Ans: Insolation and terrestrial radiation.

Ques. The average temperature of a day is termed as?

Ans: 'Daily mean temperature'.

Ques. The difference between the maximum and minimum temperatures in a day is called?

Ans: Diurnal range of temperature.

Ques. Name the instrument used for measuring the maximum and minimum temperature in a day.

Ans: Maximum-minimum thermometer.

Ques. If isotherms are plotted by connecting the places having the highest temperature on earth, it will run almost parallel to the equator. Such an imaginary line is called.

Ans: Thermal equator.

Ques. Water content in the atmosphere is called.

Ans: Humidity

Ques. How to measure absolute humidity?

Ans: It is measured as the amount of water vapour present per cubic metre volume of air (g/m³).

Ques. How many thermometer wet and dry bulb thermometer consists of?

Ans: Two

Ques. In some instances, due to rapid fall in atmospheric temperature, water vapour directly condenses to solid state (snowflakes), this is referred to as

Ans: Sublimation

Ques. Name the different forms of condensation.

Ans: Frost, Clouds, Mist/Fog and Dew.

Ques. Name the four different types of clouds.

Ans: Cirrus clouds, Stratus clouds, Nimbus clouds and Cumulus clouds.

Ques. Name the four different types of clouds based on altitude.

Ans: High clouds (20000 to 40000 ft), Medium clouds (7000 to 20000 ft), Low clouds (< 7000 ft) and Clouds with great vertical extent (2000 to 30000 ft).

Ques. When the temperature falls below 0° Celsius, the precipitation reaches the earth in the form of tiny crystals of ice, this is referred to as

Ans: Snowfall

Ques. Name the different types of rainfall.

Ans: Orographic rainfall, Convectional rainfall and border rainfall.