Humidity and Clouds

Atmospheric Moisture

Dropdown

Air rises, expands & cools on the ​

Select answer

side of a mountain



Air sinks, compresses & warms on the ​

Select answer

side of a mountain

Multiple Choice

A strong surface wind is blowing from city A toward city B. City B has a barometric pressure of 1,013 millibars. The barometric pressure of city A would most likely be

• 988 mb

• 1,002 mb

• 1,013 mb

•  1,026 mb

Multiple Choice

When the height of the mercury in a barometer is 29.92 inches, the barometric pressure is

[Use ESRT 13]

• 1,000.0 mb

• 1,005.5 m

• 1,013.2 mb

• 1,020.4 mb

Multiple Choice

Base your answer on the air pressure field map in your answer booklet and on your knowledge of Earth science. The map shows air pressures recorded in millibars (mb) at locations in eastern North America. Four isobars are shown. Points W, X, Y, and Z represent locations on Earth's surface. Letter L represents the center of a low-pressure system.

What instrument measures pressure?

• barometer

  or

  barograph

• anemometer

• sling psychrometer

• thermometer

Moisture

▪ Exists in solid, liquid, and gas in atmosphere

▪ Water enters the atmosphere by:

▪ Evaporation – liquid changes into gas
▪ Transpiration – plants release water vapor
▪ Evapotranspiration – evaporation + transpiration together

Remember it’s the SUN that provides the ENERGY

for these to occur

Match

Water enters the atmosphere by:

(match)

• Evaporation

• Transpiration

• Evapotranspiration

liquid changes into gas

plants release water vapor

evaporation + transpiration together

• liquid changes into gas

• plants release water vapor

• evaporation + transpiration together

Multiple Choice

______ provides the ENERGY for evaporation, transpiration & evapotranspiration to occur 

• Moon

• Sun

• Gnomes

• Inner Earth

Factors Affecting Evaporation

➔ Amount of energy available - (more energy = faster

evaporation). - As Energy increases, Evaporation
increases:

➔ Surface area of the water - (spread out = faster

evaporation). As SFC Area increases, Evaporation
increases:

➔ Degree of saturation - (more saturated = slower

evaporation). As degree of saturation increases,
evaporation decreases.

➔ Wind speed - greater wind speed = greater

evaporation). As Wind speed increases, evaporation
increases.

DIRECT

DIRECT

DIRECT

INDIRECT

Multiple Choice

As the amount of available energy increases, the rate of evaporation increases.

This is a ______ relationship

• Direct

• Indirect

• Cyclic

• Static

Multiple Choice

As SURFACE AREA increases, Evaporation......

• increases

• decreases

• stays the same

Multiple Choice

As degree of saturation increases, evaporation .....

• increases

• decreases

• stays the same

Multiple Choice

As Wind speed increases, evaporation ....

• increases

• decreases

• stays the same

➔ Absolute Humidity - water vapor in each unit

volume of air (AKA moisture capacity)

Warmer air holds more water vapor

than cold air

➔ Relative Humidity – ratio of the amount of

water vapor in the air to maximum amount it
can hold. Often given in forecasts

Poll

Is Dry Air or Humid Air Heavier?

• Dry air is heavier

• humid air is heavier

• The weigh the same

Poll

Would a baseball travel further on a night where the air is humid or dry?

• dry

• humid

Dry air = N2 + 02 (weight = 32= 28)

Humid air replaces some Ns and Os with H20 which weighs less!

N2 = 28

O2 = 32

H2 = 2

H2O =

Measuring Moisture

➔ Sling Psychrometer – instrument used to

indirectly measure relative humidity and dew
point

Dry bulb temp – ordinary thermometer

Wet bulb temp – thermometer with wet wick around it

Dew Point

➔ Dew Point – temperature at which air is

saturated (filled with water)

When the air temp = dew point,

then relative humidity = 100%

& condensation/PRECIPITATION occurs!

Dry Bulb = 32 °F & Wet Bulb = 24 °F. Determine the Dewpoint

Dry Bulb = 12 °Cy& Wet Bulb = 6 °C. Determine the RHy

​complete the Edpuzzle Relative Humidity & Dewpoint linked on the following slide

Edpuzzle

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To Calculate Relative Humidity & Dew Point

Use ESRT p. 12

1. Subtract: Dry Bulb – Wet Bulb

2. Locate dry bulb on left side (y-axis)

3. Locate answer to step 1 on top row (x-axis)

4.Find intersection of dry bulb row &
difference column

Make sure you are using the correct chart!

Multiple Choice

Which statement best explains why the wet-bulb thermometer of a sling psychrometer usually shows a lower temperature than the dry-bulb

• Water evaporates from the wet-bulb thermometer.

• Water vapor condenses on the wet-bulb thermometer.

• The air around the wet bulb prevents absorption of heat

• The air around the dry bulb prevents absorption of heat.

Multiple Choice

The diagram shows a sling psychrometer. Based on the dry-bulb temperature and the wet-bulb temperature, what is the relative humidity?

• 66%

• 58%

• 51%

• 12%

Multiple Choice

The diagram shows a sling psychrometer. Based on the dry-bulb temperature and the wet-bulb temperature, what is the dew point?

• 5°C

• 12°C

• 14°C

• 16°C

Multiple Choice

A student used a sling psychrometer to measure the humidity of the air. If the relative humidity was 65% and the dry-bulb temperature was 10°C, what was the wet-bulb temperature?

• 5°C

• 7°C

• 3°C

• 10°C

Multiple Choice

A sling psychrometer shows a dry-bulb reading of 14°C and a wet-bulb reading of 9°C. What are the dewpoint and the relative humidity?

A) B) C) D) 

• -10°C and 16%

• -10°C and 50%

• 4°C and 16%

• 4°C and 50%

Cloud Formation

• Air rises and cools

• Air reaches dew point & RH = 100%

• Water begins to condense (gas -> liquid)

• Water droplets form on condensation nuclei

(dust particles , aerosols, etc)

Air Masses

Air Masses

• Air Masses – large body of air in the troposphere

with similar characteristics
(pressure, moisture, temp.)

• Form when air remains stationary over an area

• Area of origin determines the
characteristics of the air mass

FOUND ON ESRT p 13

Match

Match the following

• Maritime

• Continental

• Trpical

• Polar/Arctic

Oceans/Humid

Land/Dry

Warm

Cold

• Oceans/Humid

• Land/Dry

• Warm

• Cold

Multiple Choice

Base your answer on the weather map below, which shows a weather system that is affecting part of the United States.

Compared to the air over most of the map region, the air mass centered over Alabama is

• warmer and more humid

• warmer and drier

• colder and more

• colder and drier

Multiple Choice

An air mass that originates over the northern pacific Ocean and moves southward over the United States would most likely be labeled on a weather map as

• mP

• mT

• cP

• cT

Multiple Choice

Which abbreviation indicates a warm air mass that contains large amounts of water vapor?  

• cP

• cT

• mT

• mP

Multiple Choice

Tornadoes occur when a very cold, dry air mass meets a very warm, wet air mass. Which two air masses would most likely form a tornado when they meet?

• cP and cA

• cT and mP

•  cP and mT

• mP and mT