1. AIR TEMPERATURE

2. Air temperature Periodic temp variation Horizontal temp variation
Isotherms-line connecting the points of equal temperature
Heat equator-line connecting the places having highest average temperature

3. Isotherms
Heat equator

4. Vertical temperature variation
Vertical temperature variation-regular decrease in temperature with altitude
Reasons
Major source of heat for atmosphere is the earth. So the distance from the surface of the earth increases temperature must decrease.
The density of water vapour decreases with elevation, so less heat is absorbed by the air at higher latitudes.
As the air rises to higher altitude, it extends and the temperature decreases.

5. Temperature inversion-temperature increases with an increase in height
Actual lapse rate-actual decrease in temp with elevation
Normal lapse rate-average rate of temperature decrease with elevation

6. Temperature inversion

7. Temperature measuring instruments
Maximum thermometer
Minimum thermometer
Sixes thermometer
Thermograph

8. Maximum thermometer
Minimum thermometer

9. Sixes thermometer
Thermograph