All about humidity, related key terms, factors, effects, spatial distribution, global climate etc

1. SUBMITTED BY
RAFIUL ALAM(2013135006)

2. Humidity
A measure of the
amount of water in
the air
Water is added to
the air by the process
of EVAPORATION.

3. Humidity
Humidity indicates the
likelihood of
precipitation, dew, or
fog.
Humidity is as well
as relative humidity
measured in %
The amount of
water that is
actually in the air
measured in g/mᵌ

4. Humidity
Absolute
Relative
specific
Types Of Humidity

5. ABSOLUTE HUMIDITY: Absolute humidity (expressed as grams of water
vapor per cubic meter volume of air) is the mass of water in the air.
Types Of Humidity

6. • RELATIVE HUMIDITY is the amount of water in the
air compared to the amount of water the air could
possibly hold.
• Humidity values are usually given as Relative Humidity.
Examples:
if the air is holding half the water it could hold, it’s Relative
Humidity is 50%.
If the air is holding no water, relative humidity is 0%
If it holding a quarter of the water it could hold, 25%
Types Of Humidity

7. Factors that Affect Relative Humidity
•Amount of water: If you increase the
amount of water in the air (by adding it due
to evaporation), Relative humidity will go up.
•Temperature: Since warm air can hold more
water than cold air, if you lower the
temperature the Relative Humidity will go up,
even if you don’t add more water.
Types Of Humidity

8. • Specific humidity is the ratio of the mass of water vapor to the total
mass of the moist air parcel.
• Water (mass) mixing ratio is the mass of water vapor compared to
mass of dry air
Types Of Humidity

9. Temperature vs Relative Humidity

10. Temperature vs Relative Humidity

11. If the air is holding ALL the water it can hold it is saturated
and the relative humidity is 100%
Saturation

12. • DEW POINT is the temperature at which
condensation will occur. The Dew point is the
temperature the air must be in order to be
saturated.
Dew Point

13. Dew Point

14. Dew Point

15. • WARM AIR CAN HOLD MORE WATER VAPOR THAN COLD AIR, so
with the same amount of absolute/specific humidity,
• cooler air will have a HIGHER relative humidity, and warmer air a
LOWER relative humidity.
6/12 *100=50% 6/24*100=25%
Facts

16. Water capacity of air at different temperatures

17. What temperature can hold more water vapor?

18. • Relative Humidity is measured using a PSYCHROMETER.
– A psychrometer is made of two thermometers. One is
covered with a wet cloth. When air moves over the wet cloth,
evaporation occurs and lowers the temperature on that
thermometer. If you compare the temperature on the two
thermometers you can get the relative humidity.
Measuring Humidity

19. • In the area of the vegetation, relative humidity is high whereas in the
bare land there is less moisture and relative humidity is also less.Vegetation
• The relative humidity increases as the altitude increases. Because as we
go higher, there is the decrease in the temperatureAltitude
• At the higher elevation than 800m relative humidity is less compared to
sea level.Orographic effect
• The average maximum diurnal relative humidity occurs in early morning
and the minimum diurnal humidity occurs in the early afternoon.Transfer of humidity
Factors which affect the humidity

20. Humidity affects global climate in in two major ways.
• First, water vapor in the atmosphere contains "latent" energy. During
transpiration or evaporation, this latent heat is removed from surface liquid,
cooling the earth's surface. This is the biggest non-radiative cooling effect at
the surface. It compensates for roughly 70% of the average net radiative
warming at the surface.
• Second, water vapor is the most abundant of all greenhouse gases. It absorbs
the infrared energy emitted (radiated) upward by the earth's surface.This
selective absorption causes the greenhouse effect.
Global Climate

21. Animals and
plant
Human
comfort
Electronics
Building
construction
Industry
Effect Of Humidity

22. Effect Of Humidity

23. Spatial distribution
• The most humid cities on earth are generally located closer to the equator, near
coastal regions.
• Cities in South and Southeast Asia are among the most humid. Kuala Lumpur,
Jakarta, and Singapore have very high humidity all year round because of their
proximity to water bodies and the equator and often overcast weather. Some
places experience extreme humidity during their rainy seasons such as Kolkata,
Chennai and Cochin in India, and Lahore in Pakistan.
• Sukkur city located on the Indus River in Pakistan has some of the highest and
most uncomfortable dew point in the country frequently exceeding 30 °C (86 °F)
in the Monsoon season.
• Shanghai and Hong Kong in China also have an extreme humid period in their
summer months.
• In cooler places such as Northern Tasmania, Australia, high humidity is
experienced all year due to the ocean between mainland Australia and Tasmania.
• The most humid cities on earth are generally located closer to the equator, near
coastal regions.
• Cities in South and Southeast Asia are among the most humid. Kuala Lumpur,
Jakarta, and Singapore have very high humidity all year round because of their
proximity to water bodies and the equator and often overcast weather. Some
places experience extreme humidity during their rainy seasons such as Kolkata,
Chennai and Cochin in India, and Lahore in Pakistan.
• Sukkur city located on the Indus River in Pakistan has some of the highest and
most uncomfortable dew point in the country frequently exceeding 30 °C (86 °F)
in the Monsoon season.
• Shanghai and Hong Kong in China also have an extreme humid period in their
summer months.
• In cooler places such as Northern Tasmania, Australia, high humidity is
experienced all year due to the ocean between mainland Australia and Tasmania.

26. GLOBAL RELATIVE HUMIDITY

29. THANK YOU