# GEOG 1101 Lecture 3: geog LESSON 3

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7 Feb 2017
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ECOL LESSON THREE
By adding water vapor to air ( T° held constant)
air T° 25°C 25°C 25°C
Sp. Hum. 5gm/kg 10gm/kg 20gm/kg
capacity 20gm/kg 20gm/kg 20gm/kg
R.H. 25% 50% 100%
{(5/20)X100}
By cooling the air T° (water vapor content held constant)
air T° 30°C 20°C 15°C
Sp. Hum. 10gm/kg 10gm/kg 10gm/kg
capacity 27gm/kg 14gm/kg 10gm/kg
R.H. 37% 71% 100%
{(10/27)X100}
** When the R.H. varies during the day, it's because of a change in air temperature OR a change
in the amount of water vapor in the air * The
most common way and easiest way for the RH of the air to be changed is by changing the air
temperature.
* This is also the most common & easiest way for the air to become
saturated and thus for condensation to occur, by changing the air T°.
** Water vapor content in the air and thus RH varies from day to day,
month to month, seasonally and spatial (from place to place).
* Remember, the colder the air, the less water vapor it can hold.
While the warmer the air, the more water vapor it can hold.
__________________________________________________________________________
In meteorology the term adiabatic refers to a parcel of air changing temperature without heat energy
** A parcel of air that contains warm air is less dense (lighter) and thus
may rise. As this parcel of air rises in the atmosphere, it will
encounter lower pressure and thus expand. As it expands the
molecules in it will start to slow down and thus kinetic energy
levels will decrease. As this occurs, the T° will also decrease.
** Conversely, a parcel of cold air is more dense (heavier) and thus sinks.
As this parcel of air sinks in the atmosphere, it will encounter higher
pressure and thus be compressed. As it is compressed the molecules
in it will start to speed up and thus kinetic energy levels will increase.
As this occurs, the will also increase.
So, Expanding air = Tº decrease
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