Module 4

Question 1

Adiabatic vs diabatic

Answer 1

Adiabatic: change of temperature without change of state
Diabatic: change of state without change of temperature

Question 2

Super adiabatic lapse rate

Answer 2

Any ELR greater than 3°c/ 1000’ produces extreme instability

Question 3

Convective stability/instability

Answer 3

Unstable: lower layer wet and upper layer dry
Stable: lower layer dry upper layer wet
SALR cools slower due to latent heat

Question 4

Diurnal stability/instability

Answer 4

Unstable mornings due to land heating faster than air above it
Stable evenings due to land/low level cooling faster than atmosphere

Question 5

Saturation

Answer 5

100% RH
Rate of condensation equal to rate of evaporation

Question 6

Vapour pressure and saturation vapour pressure

Answer 6

Vapour pressure: actual contribution of vapour to a pressure in given volume
Saturated vapour pressure: maximum potential contribution of wv in given volume and temp if saturated

Question 7

4 primary cloud triggers

Answer 7

Convection
Convergence (helps to uplift already unstable air)
Orographic
Frontal

Question 8

Latent heat contribution to CB

Answer 8

As cloud forms and water condenses latent heat is realeased increasing instability and adding fuel to continued rising and instability and production of vertical CB

Question 9

Cloud types and heights tropics and mid latitude

Answer 9

High clouds: ci, cs, cc
Mid lat Height: 20000’ to top of tropopause
Tropic height: 25000’ to top trop

Middle cloud: as, ac, ns
Mid lat height: 6500 to 20000’
Tropic height: 6500-25000’

Low cloud: st, sc,cu, tcu, cb
Mid lat and tropic height: surface to 6500’

Unstable air creates healed clouds stable air forced up creates layer clouds

Question 10

Cloud dispersal factors

Answer 10

Sinking or gravitational settling: air is being pulled down increasing pressure and heating adiabatically pushing it away from dew point

Direct warming (insolation or terrestrial radiation): heating from below increases atmospheric temps making it harder for the air to saturated. Heating from above prevents air from rising any higher and cutting off condensation processes dispersing clouds horizontally.

Entrainment ( mixing with clear air): dry outside air mixes with saturated air eating at the edges of the cloud and reducing RH

Question 11

Calculating cloud base CCL and LCL

Answer 11

LCL is forced lifting of dry air (dalr)
LCL= (400 x (st - dp) x 0.85
St= surface temp
Dp= dew point

CCL is convective lifting of unstable air ( start at higher temp and therefore must travel higher before cloud forms)
CCL = 400 x (st - dp)

Question 12

Pressure laps rate equation

Answer 12

PL = 96Tk/Phpa

Question 13

Bergeron theory

Answer 13

Most cloud droplets never precipitate to the ground because they are incredibly small and round. Large surface area due to roundness means lots of potential evaporation. In order to precipitate to surface condensation rates must match or exceed evaporation rates

For bergeron to exist need a vapour pressure vs temperature environment where freezing level and supercooled water both exist creating snow. Super cooled water freezes onto ice crystal nuclei eventually leaving only ice or snowflakes and no scwd

Question 14

Coalescence theory

Answer 14

Big drops attract and consume small drops
Collisions: larger body falls or rises slower than smaller bodies colliding on the way
Sweeping: large drop creates low pressure in its wake pulling small drops in

Question 15

Freezing rain

Answer 15

Forms when snow or scwd falls through warm layer and melts but remains super cooled and enters subzero layer near ground freezing on impact
Common downstream of mountainous terrain

Question 16

Factors effecting precipitation rates

Answer 16

Gravity
Up/down draft speed
Droplets size and mass: maximum speed increases with size (mass increases with cube of drop size, air resistance increases slower with the square of drop size)
0.2-0.5 mm diameter: 0.7-2 m/s
0.6-4 mm diameter: 2-9m/s
4-5 mm or larger: 9-13 m/s