Movement Of An Air Parcel Flashcards
Feedback effects
- 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. 
Relative humidity
- 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 
When air parcels are stable…
They stay where they are
When air parcels are unstable
They move position until they are stable
Low pressure…
- surface air convergence
- ascent
- air divergence
High pressure
- upper air convergence
- subsidence
- surface air diverges
Environmental lapse rate
- 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. 
Movement of an air parcel
- Newton’s second law of motion
- no net force = body stays constant
- net force = body moves at constant
Diabatic cooling
- the horizontal movement of an air parcel
- no change in volume or pressure by energy (temp) is lost to surroundings by turbulence or conduction.
Adiabatic cooling
- 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.
Dry adiabatic lapse rate
- 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)
Saturated adiabatic lapse rate
- wet air is warmer than dry air irrespective of pressure and volume
Continentality and oceanicity
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
Main forces controlling oceans and atmospheric circulation
1: pressure gradient force
2: centrifugal force
3: Coriolis force
4: geostrophic force
5: friction (Ekman balance)
Pressure gradient force
- mainly horizontal movement
- wind flows according to PGF
- isobars = lines of equal atmosphere pressure
Centrifugal force and centripetal force
Centrifugal = internal force
Centripetal force = fundamental static force
Coriolis force
- 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
Geostrophic balance
The balance between the Coriolis and pressure gradient force
Friction
Friction causes turbulence which generates heat and energy dispersal which slows fluid flow
Ekman balance
- 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
Forces are more important on atmos than oceanic circulation because?
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.
Boundary Layer
- 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.
Planetary boundary layer
- 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.
Describe the diurnal changes of the PBL
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.)
