Geography 101 Quiz 7

Front 1

What are clouds?

Back 1

"Moisture droplets suspended in the air”

Front 2

Two conditions for cloud formation:

Back 2

- Saturation (reaches 100% relative humidity)

- surface on which vapour can condense

note: adiabatic process most important in cloud formation

Front 3

Hydroscopic (water seeking) nuclei

Back 3

salt from sea water
products from combustion

Front 4

Hydrophobic (water-repelling) nuclei

Back 4

dust, pollen, volcanic eruptions
explains why it always rains when volcanoes erupt

Front 5

Cumulo Nimbus

Back 5

if asked on test what cloud is related to severe weather, this is always it!

Forms severe weather when trying to equilibriate.

Front 6

What is a contrail? how does it meet the requirements for forming a cloud?

Back 6

a) come from jets
b) High clouds
greenhouse enforcing, trap Ldown but do not reflect albedo
c) scientists measured the effect of contrails after September 11th because there were no jets in the air
d) Meet condtions to be considered a cloud!
Moist air causes saturation
sulfate molecules from exhaust become condensation nuclei (so allow a surface to condense on)

Front 7

What is the difference between mist and fog?

Back 7

i. if visibility is restricted to less than 1km, it's a fog

ii. reporters on the radio always get them mixed up

Front 8

what is fog?

Back 8

Fog – cloud layer on the ground, with visibility restricted to less than 1 km (vs. mist)
Indicates saturated conditions: air temp and dew point temp at ground level are nearly identical
Almost all fog is warm – moisture droplets are above freezing

Front 9

types of fog

Back 9

based on how 100% RH is achieved
Decreasing temperature: Cooling
Radiation fog
Advection fog
Upslope fog

Front 10

Radiation Fog on moist grounds clear nights

Back 10

radiative cooling of a surface chills the air layer above that surface to dew point temperature

Front 11

Valley Fog

Back 11

An advection fog associated with topography of area.
Cool dense air settles in low-lying areas where it is chilled and saturated near the ground

Front 12

ice crystal fog

Back 12

At low temperatures in continental arctic air mass
Air becomes full of ice crystals formed by sublimation

Front 13

advection fog

Back 13

Warm moist air migrates to a cooler place
The migrating air becomes chilled to dew point and fog develops

Front 14

Upslope fog

Back 14

on mountain, as air goes up temperature goes down until 100% relative humidity is reached

Moist air flows toward slope; as air rises with the terrain, it cools to condensation temperature. Fog forms on the slope.

Front 15

How precipitation forms

Back 15

Cloud formation – cooling air condenses water vapour to water in the presence of cloud-condensation nuclei

Two theories - Bergeron Process and Collision-Coallescence process

Front 16

lake fog

Back 16

cool air on top of warm water

Front 17

The Bergeron Process

Back 17

Precipitation from cold clouds

a) high in the atmosphere water droplets become super cooled and not frozen. They become frozen when they impact the surface (so when they attach to nuclei and become solid).
b) Ice crystals fall and melt to produce rain
c) if the surface is cold, becomes snow instead


In the cloud
Water droplets do not freeze at 0oC (super cooled)
will freeze at - 40oC when it impacts an object
Will freeze in contact with freezing nuclei (crystal form)
Freezing nuclei becomes active at -10oC
So water and ice co-exist
Droplet is saturated (but solid ice is not saturated)
So net transfer from liquid droplet to solid ice crystal
Snow crystals grow and descend
Intercept droplets that freeze on them
Large snowflakes (precipitation)

Front 18

The Collision-Coalescence Process

Back 18

Precipitation from warm clouds

i. droplets break up and coalesce, growing in size, as they bump into each other
a) So basically as water droplets fall, they bump into each other and get bigger
ii. Why do they collide? (on quiz)
a) bigger nuclei fall faster
b) Bumping because there are more molecules to stick to
c) so burning more fuels puts more nuclei in atmosphere and causes more rain



Large droplets form when “giant” condensation nuclei are present
Hygroscopic
Larger droplets fall , collide with smaller, slower droplets and coalesce
Grow in size
Break up
Collide and coalesce
Grow in size
Tropics: air is humid and clean (less nuclei) meaning lesser but bigger droplets

Front 19

Why does dew form on plants more than elsewhere?

Back 19

a) Plants add to moisture and raise RH.
b) Caused by transpiration from plants

Front 20

Dew

Back 20

forms in morning because relative humidity reaches 100%

condensation of water vapour on objects that have radiated sufficient heat to lower their temperature below the dew point of the surrounding air
Differential formation of dew: different objects radiate heat differently

Front 21

How is frost formed?

Back 21

Forms when dew point of the air is below freezing
Deposition: water changes from gas to solid
ii. not frozen dew!!

Front 22

adiabatic temperature changes

Back 22

A. Cooling or warming of air is caused when air is allowed to expand or air is compressed, not because heat is added or subtracted.
i. As air warms it expands, molecules are less dense and don't bump into each other. If molecules don't collide, temperature decreases

Front 23

What is a parcel?

Back 23

body of air with a specific temperature and humidity

Front 24

Dry Adiabatic Rate (DAR)

Back 24

as air parcel raises, drops at rate of 10 degrees Celsius per 1000 metres

Front 25

LCL

Back 25

Lifting Condensation Level

a) height at which parcel reaches saturation
b) RH gets higher with altitude as it gets cooler

Front 26

Wet Adiabatic Rate (WAR)

Back 26

a) rate will be between (5-9 degrees celsius per 1000 kms)
b) ***** if rate is not provided on test, always use 6 degrees celsius per 1000 kms
c) Reduced cooling due to release of latent heat of condensation
condensation releases latent heat, so instead of raising by 10 degrees, raises by 6

Front 27

Atmospheric stability

Back 27

Compare temperature of parcel to temp of surrounding air.

Stability: tendency of air parcel to remain in place or change vertical position (rise/fall)

Front 28

absolute stability

Back 28

does not rise when stable

Front 29

absolute instability

Back 29

unstable air – starts the same, different rate of cooling causes instability

Front 30

four types of conditional instability

Back 30

a) Orographic lifting (moves towards mountain)
b) converging winds
c) two fronts meeting
d) convection – energy from warmth of Earth