Chapter 17

Question 1

How is heat energy measured?

Answer 1

Measured in calories – one calorie is the heat necessary to raise the temperature of 1 gram of water 1 degree Celsius

Question 2

What is latent heat?

Answer 2

Stored or hidden heat
Not derived from temperature change
Important in atmospheric processes

Question 3

Describe evaporation

Answer 3

Liquid is changed to gas

600 calories per gram of water are added – called latent heat of vaporization

Question 4

Describe condensation

Answer 4

Water vapor (gas) is changed to a liquid 
Heat energy is released – called latent heat of condensation

Question 5

Describe melting

Answer 5

Solid is changed to a liquid

80 calories per gram of water are added – called latent heat of melting

Question 6

Describe freezing

Answer 6

Liquid is changed to a solid

Heat is released – called latent heat of fusion

Question 7

Describe sublimation

Answer 7

Solid is changed directly to a gas (e.g., ice cubes shrinking in a freezer)
680 calories per gram of water are added

Question 8

Describe deposition

Answer 8

Water vapor (gas) changed to a solid (e.g., frost in a freezer compartment)  
Heat is released

Question 9

Describe humidity

Answer 9

Amount of water vapor in the air
Saturated air is air that is filled with water vapor to capacity
Capacity is temperature dependent – warm air has a much greater capacity
Water vapor adds pressure (called vapor pressure) to the air

Question 10

What is “Mixing Ratio” in relation to humidity

Answer 10

Mass of water vapor in a unit of air compared to the remaining mass of dry air
Often measured in grams per kilogram

Question 11

What is relative humidity?

Answer 11

Ratio of the air’s actual water vapor content compared with the amount of water vapor required for saturation at that temperature (and pressure)

Question 12

How can the relative humidity be changed?

Answer 12

-Add or subtract moisture to the air
Adding moisture raises the relative humidity
Removing moisture lowers the relative humidity
-Changing the air temperature
Lowering the temperature raises the relative humidity

Question 13

What is a dew point temperature?

Answer 13

Temperature to which a parcel of air would need to be cooled to reach saturation

Question 14

What do we use to measure humidity, and what are the two types?

Answer 14

Hygrometers- Psychrometer, Hair hygrometer

Question 15

What is a Psychometer?

Answer 15

compares temperatures of wet-bulb thermometer and dry-bulb thermometer
If the air is saturated (100% relative humidity) then both thermometers read the same temperature
The greater the difference between the thermometer readings, the lower the relative humidity

Question 16

What is a hair hygrometer?

Answer 16

reads the humidity directly

Question 17

When do adiabatic temperature changes occur?

Answer 17

When air is compressed, when air expands,

Question 18

What is the Dry adiabatic rate?

Answer 18

Unsaturated air
Rising air expands and cools at 1˚C per 100 meters (5.5˚F per 1,000 feet)
Descending air is compressed and warms at 1˚C per 100 meters

Question 19

What is the wet adiabatic rate?

Answer 19

Commences at condensation level
Air has reached the dew point
Condensation is occurring and latent heat is being liberated
Heat released by the condensing water reduces the rate of cooling
Rate varies from 0.5˚C to 0.9˚C per 100 meters

Question 20

What is Oragraphic lifting?

Answer 20

Elevated terrains act as barriers

Result can be a rainshadow desert

Question 21

What is frontal wedging?

Answer 21

Cool air acts as a barrier to warm air

Fronts are part of the storm systems called middle-latitude cyclones

Question 22

What is Convergence?

Answer 22

where the air is flowing together and rising (low pressure)

Question 23

What is localized convective lifting?

Answer 23

Localized convective lifting occurs where unequal surface heating causes pockets of air to rise because of their buoyancy

Question 24

What are the types of stability with air?

Answer 24

Stable air, absolute instability, conditional instability
Determines to a large degree
Type of clouds that develop
Intensity of the precipitation

Question 25

Describe stable air

Answer 25

``` Resists vertical displacement Cooler than surrounding air Denser than surrounding air Wants to sink No adiabatic cooling Absolute stability occurs when the environmental lapse rate is less than the wet adiabatic rate ```

Question 26

Describe absolute instability

Answer 26

``` Acts like a hot air balloon Rising air Warmer than surrounding air Less dense than surrounding air Continues to rise until it reaches an altitude with the same temperature Adiabatic cooling Environmental lapse rate is greater than the dry adiabatic rate Clouds are often towering ```

Question 27

Describe conditional instability

Answer 27

occurs when the atmosphere is stable for an unsaturated parcel of air but unstable for a saturated parcel

Question 28

What are condensation nuclei?

Answer 28

Possible condensation surfaces in the atmosphere are called condensation nuclei Dust, smoke, etc. Ocean salt crystals that serve as hygroscopic (“water seeking”) nuclei

Question 29

What are the three basic forms of clouds and describe them

Answer 29

Cirrus – high, white, thin Cumulus – globular cloud masses often associated with fair weather Stratus – sheets or layers that cover much of the sky

Question 30

How do we classify clouds

Answer 30

Based on hight - High, middle, lower

Question 31

What does Nimbus mean

Answer 31

Rainy

Question 32

Why does most fog form?

Answer 32

Radiation cooling, or movement of air over a cold surface

Question 33

How does advection fog form?

Answer 33

Warm, moist air moves over a cool surface

Question 34

How does radiation fog form?

Answer 34

Earths surface cools rapidly. Forms during cool, clear, calm nights

Question 35

How does upslope fog form?

Answer 35

Humid air moves up a slope, adiabatic cooling occurs

Question 36

How does steam fog form?

Answer 36

Cool air moves over warm water and moisture is added to the air Water has a steaming appearance

Question 37

How does frontal fog, or precipitation fog, form?

Answer 37

Forms during frontal wedging when warm air is lifted over colder air Rain evaporates to form fog

Question 38

What is the Bergeron process?

Answer 38

Temperature in the cloud is below freezing Ice crystals collect water vapor Large snowflakes form and fall to the ground or melt during descent and fall as rain

Question 39

What is the Collision-coalescence process?

Answer 39

``` Warm clouds Large hygroscopic condensation nuclei Large droplets form Droplets collide with other droplets during their descent Common in the tropics ```

Question 40

What are the forms of precipitation?

Answer 40

Rain, Snow, Sleet, Hail, Rime

Question 41

What is the general ration for the water equivalent of snow?

Answer 41

10 snow units to 1 water unit