Topic:
Moisture in the Atmosphere
Water enters the Atmosphere by
A) ---
Mainly from
Ocean
70% Earth’s
surface
Factors Effecting Evaporation Rate
a) Surface Temperature Increases 
---
b) Surface Area Increases 
---
Evaporation
Puddle A
Evaporation
Puddle B
c) Humidity increases 
--Air is filled with
water, no more
evaporation.
Evaporation
Lake
d) Wind Speed Increases ->
---
Lake
B) ---
Evaporation and Transpiration
= Evapotranspiration
Water is found in all phases in the
atmosphere
Solid – Clouds, snow
2) Liquid – Clouds, rain
3) Gas - Water vapor
1)
How do we measure moisture
in the Atmosphere
Humidity
 ---
Relative Humidity

---

---
Dew Point
 ---
Condensation
What happens when the air temperature
and dew point are the same?
Sublimation / Deposition
FROST
SNOW
Tools used to find Dew Point & Relative Humidity
-----
Measuring Relative Humidity
Today you need your ESRT out
Dew Point & Relative
Humidity Charts
Best Friend - pg 12
The “Dry Bulb” = Air Temp

Don’t let it fool you. It is
just a thermometer.
20°C
The “Wet Bulb”
Has a little wet booty
tied to the bottom.
 Gets cool when water
evaporates.

Wet Booty
12°C
A Dry Day…
A lot of moisture
will evaporate.
 The wet bulb will
be a lot cooler
than the dry bulb.

20°C
Difference between wet bulb
& dry bulb is 12 °C.
20°C
14°C
12°C
8°C
A Humid Day…
A little bit of
moisture will
evaporate.
 The wet bulb will
not be much
cooler than the
dry bulb.

20°C
Difference between wet bulb
& dry bulb is 6 °C.
14°C
Dry-bulb temperature = air temperature.
20 °C
14 °C
Subtract (the difference) between the dry bulb and wet bulb
20°C
14°C
20-14=6
18°C
16°C
18-16=2
Put it all together
20°C
8°C
20-8=12
Relative Humidity = 11%
14°C
10°C
14-10=4
Relative Humidity = 60%
The Dew Point Chart works the same way
14°C
10°C
14-10=4
Dew Point = 6°C
Try These.
Dry Bulb
Wet Bulb
26°C
20 °C
14 °C
14 °C
0 °C
-3 °C
R Humidity DPT
%
%
%
°C
°C
°C
Dry Bulb
Wet Bulb
21°C
19°C
17 °C
17°C
70°F °C 60 °F °C
R Humidity DPT
%
%
%
°C
°C
°C