Movement Of An Air Parcel

Question 1

Feedback effects

Answer 1

• What goes into a system must come out through clouds aerosols O-Zone et cetera
• Aerosols: Anything released it is taken into the atmosphere and attaches to cloud droplets et cetera. 

Question 2

Relative humidity

Answer 2

• The amount of moisture an air parcel contains compare to what it can contain given its pressure and temperature.
• Anything relative is dependent on something example pressure or temperature
• Ambient air 

Question 3

When air parcels are stable…

Answer 3

They stay where they are

Question 4

When air parcels are unstable

Answer 4

They move position until they are stable

Question 5

Low pressure…

Answer 5

• surface air convergence
• ascent
• air divergence

Question 6

High pressure

Answer 6

• upper air convergence
• subsidence
• surface air diverges

Question 7

Environmental lapse rate

Answer 7

• The rate of decrease in temperature with altitude and the ambient atmosphere at a given time and location
• The temperature of the atmosphere is largely determined by the ELR of surrounding ambient air.
• If the temperature of the air parcel is the same as the temperature of surrounding the parcel is stable in stays where it is.
• If there is a change in temperature of the air parcel is unstable and will continue to rise or fall. 

Question 8

Movement of an air parcel

Answer 8

• Newton’s second law of motion
• no net force = body stays constant
• net force = body moves at constant

Question 9

Diabatic cooling

Answer 9

• the horizontal movement of an air parcel
• no change in volume or pressure by energy (temp) is lost to surroundings by turbulence or conduction.

Question 10

Adiabatic cooling

Answer 10

• the air parcel increases in volume due to decreased density of ambient air which causes a decrease in temperature.
• where there is a change in temp without a loss of energy to surroundings.
• dependent on change in pressure and density
• change in pressure impacts density but the two don’t work together.
• will also increase density within the parcel.

Question 11

Dry adiabatic lapse rate

Answer 11

• if the air is dry as it rises it will cool at the DALR (-9.8 degrees C km-1)
• If the DALR decreases in temp during rise of the air parcel is less than the decrease in temp in the surrounding air then the air parcel is unstable and will continue to rise.
• interactions between pressure, temp, and volume of an air parcel and conditions of surrounding atmosphere may promote sinking.
• moisture within the air parcel condenses (release of lantern heat which means the air parcel cools more slowly than the DALR)

Question 12

Saturated adiabatic lapse rate

Answer 12

• wet air is warmer than dry air irrespective of pressure and volume

Question 13

Continentality and oceanicity

Answer 13

C = how climate of a place is affected by its remoteness from the oceanic air
O = the degree to which the climate of a place is influenced by the sea

Question 14

Main forces controlling oceans and atmospheric circulation

Answer 14

1: pressure gradient force
2: centrifugal force
3: Coriolis force
4: geostrophic force
5: friction (Ekman balance)

Question 15

Pressure gradient force

Answer 15

• mainly horizontal movement
• wind flows according to PGF
• isobars = lines of equal atmosphere pressure

Question 16

Centrifugal force and centripetal force

Answer 16

Centrifugal = internal force
Centripetal force = fundamental static force

Question 17

Coriolis force

Answer 17

• force generated as a result of the earths spin on its axis from west to east.
• force is largest at the poles and zero at the equator.
• force causes objects to be deflected from their paths

Question 18

Geostrophic balance

Answer 18

The balance between the Coriolis and pressure gradient force

Question 19

Friction

Answer 19

Friction causes turbulence which generates heat and energy dispersal which slows fluid flow

Question 20

Ekman balance

Answer 20

• the interaction between the Coriolis force and friction working against the PGF in the direction of geostrophic force.
• higher part of the atmos = geostrophic winds dominate
• lower part of atmos = higher friction, PGF dominates

Question 21

Forces are more important on atmos than oceanic circulation because?

Answer 21

1: boundaries are more fixed in the ocean
2: air is less dense than water
3: the atmos is thicker than the ocean.
4: global scale atmos circulation can be pretty accurately forecasted and modelled.

Question 22

Boundary Layer

Answer 22

• where solar radiation is absorbed
• long wave radiation is emitted
• turbulent fluxes of sensible and latent heat originate
• below 10km (the troposphere)
  Weather including mid-latitude disturbances is contained.

Question 23

Planetary boundary layer

Answer 23

• also known as the atmospheric boundary layer (ABL)
• characterised by the mechanically induced turbulence due to the friction drag from airflow over rough surface and by convectively induced turbulence caused by thermal instability.
• turbulence is responsible for the fluxes of heat and moisture to and from the surface.
• PBL height varies by place, surface type, time of day, years as well as atmospheric conditions.

Question 24

Describe the diurnal changes of the PBL

Answer 24

During the day: solar radiation heats the ground causing thermal instability and buoyant plumes of rising air that increases the depth of the PBL.
During the night: surface cooling dominates the radiation regime and the PBL depth increases to less than 100m in depth.

• under strong wind conditions the turbulence is forces more by airflow over rough terrain and diurnal variations would be weakened.)

Question 25

Laminar boundary layer

Answer 25

• lowest layer within a few mm or the surface.
• air is laminar and not turbulent
• this layer adheres to all surfaces creating a buffer between the surface and the turbulence layer beyond.
• all fluxes which go from the surface to the atmos must travel through this layer.
• transfer is done by conduction.

Question 26

Characteristics of the roughness layer

Answer 26

• below the surface layer where direct of the surface roughness elements dominate
• height of the roughness layer is typically 2-3 times the height of the roughness elements
• turbulence has not yet broken down the irregularities caused by the roughness elements into homogeneous turbulence.

Question 27

atmospheric motion

Answer 27

• horizontal temperature variations give rise to horizontal pressure difference that result in air motion (winds)
• thermal energy is converted into kinetic energy (winds)
• kinetic energy cascades to smaller and smaller scales of motion due to turbulence.

Question 28

What are eddies and what type of eddies are there

Answer 28

Eddies = whirl of air caused when wind encounters a solid object (eg mountain)
- mechanically generated eddies= forced convection due to surface roughness and wind shear.
- thermally generated eddies = free convection due to buoyancy.
- large eddies = buoyancy generated
- smaller eddies = roughness generated

Question 29

Atmospheric stability

Answer 29

• the tendency of air to move by buoyant convective processes arising from density differences

Question 30

Saturation of the air

Answer 30

• refers to the equilibrium condition where the rate of the evaporation into air equals the rate of condensation out of the air.
• when air is saturated, evaporation can still take place as long as the condensation of the same amount takes place.
• the amount of water vapour present in the atmosphere at saturation depends on temperature, ice vs water surface that molecules enter or leave.

Question 31

Boyles law

Answer 31

• the relationship between pressure and volume are nearly constant
• determines the stability of the fluid
• fluid depends on density and gradient
• airflow = northerly
• water flow = southerly