Revision: Atmosphere Geography (English Medium) ICSE Class 9 CISCE

These are chloro-fluoro carbons and are used as propellants in aerosol cans, refrigerants in refrigerators, air conditioning and as solvent cleaners in the microelectronic industry.

Atmosphere is a thin blanket of air that surrounds the earth. It protects us from the harmful rays of the sun. It consists of several gases in which nitrogen and oxygen occupy the major portion.

The topmost layer of the atmosphere is called the Exosphere.

The layer of the atmosphere which extends to a height of 80 km above the stratosphere is called Mesosphere.

The ionosphere, which extends from 80 km to 480 km is known as the Thermosphere.

The envelope of air around the Earth is called the atmosphere. It is composed of nitrogen, oxygen, water vapour, and carbon dioxide, with other gases present in small quantities. The atmosphere is like a protective blanket that keeps our planet safe and helps support life. 

The upper limit of the troposphere is called Tropopause.

The large depletion of ozone layer in certain parts of the atmosphere is called Ozone hole.

The layer of the atmosphere above the troposphere is called Stratosphere.

The atmospheric layer closest to the earth is called Troposphere.

Daily Mean Temperature - The average of the maximum temperature and minimum temperature recorded during a day (24 hours) is known as daily mean temperature.
Daily Mean Temperature = `("Max. Temp. + Min. Temp.")/2`

For example, if a place has a maximum temperature of 39°C and a minimum temperature of 27°C for a particular day, the daily mean temperature.

`=(39^circ+27^circ)/2 = 66^circ/2 = 33^circ"C"`

Mean Temperature of a place — The mean temperature of a place is obtained by collecting the data for a period of 30 – 40 years. The average mean annual temperature of a place is calculated. This is also known as the normal temperature of a place.
Mean temperature = `" Mean Annual Temp. of 1986+1985......for 35 years"/35`

Annual Mean Temperature — The average of the daily mean temperature of all days of a year is known as Annual mean temperature.
The annual mean temperature of the year 2010 = `" Daily mean temp. of 1+2+3......365 days"/365`

Monthly Mean Temperature — The average of the daily mean temperature of all days of a month is known as the monthly mean temperature.
The monthly mean temperature of July = `"Daily mean temp. of 1+2+3......31 days"/31`

The pressure exerted by this mercury column is considered as the pressure of magnitude ‘one atmosphere’ (1 atm).

A low-pressure area is an area in the atmosphere where the pressure is lower than its surrounding areas. In this situation, the wind from the surroundings blows towards the center of low pressure.

High pressure is an area of the atmosphere where the barometric pressure is higher than its surrounding areas. In this case, the wind from the center of high pressure blows towards the surrounding low-pressure areas.

Pressure gradient is defined as the decrease in pressure per unit distance in the direction in which the pressure decreases most rapidly.

Air flows from areas of high pressure to areas of low pressure.

The height of a place above the mean sea level is known as its altitude.

 Monsoons are the periodic seasonal winds blowing in the regions of South East Asia and Northern Australia. The word monsoon is derived from the Arabic word ‘Mausim’ meaning ‘Season’, on account of deeply affecting the seasons of the particular region.

This force is created by the rotation of the earth as the winds in different belts deflect towards the right in the Northern Hemisphere and to the left in the Southern Hemisphere.