Atmospheric Stabilty Flashcards
Moisture exists in 3 states:
- Solid (ice crystals) - snow and frost and hail
- Liquid (water)
- Gas (water vapour)
Changes of state:
exchange of latent heat occurs in all changes of state
- Solid to Liquid
Melting (addition of latent heat)
Changes of state:
exchange of latent heat occurs in all changes of state
- Liquid to Gas
Evaporation (addition of latent heat)
Changes of state:
exchange of latent heat occurs in all changes of state
- Gas to Solid
Deposition (release of latent heat)
Changes of state:
exchange of latent heat occurs in all changes of state
- Solid to Gas
Sublimation (addition of latent heat)
Changes of state:
exchange of latent heat occurs in all changes of state
- Gas to Liquid
Condensation (release of latent heat)
Changes of state:
exchange of latent heat occurs in all changes of state
- Liquid to Solid
Freezing (release of latent heat)
What is latent heat?
The heat which must be added or released to change a substance to a higher or lower state
What is humidity?
How is it measured?
How is relative humidity expressed?
The amount of water vapour contained in a sample or air.
Using a psychrometer or hygrometer
As a percentage of water vapour present in a sample of air compared to the maximum amount that the air could hold at that temp. and pressure
What is dew point?
The temperature to which a sample of air must be cooled to reach saturation
Define adiabatic:
When the temperature of a sample of air changes to a change in pressure or volume (without change in the total heat of an air sample)
What temperature is the Dry Adiabatic Lapse rate (DALR)?
What temperature is the Saturated Adiabatic Lapse rate (SALR)?
3C per 1000FT
1.5C per 1000FT
What is a stable atmosphere?
What does stability or instability depend on?
One in which a parcel of air returns to its original level after being forced vertically due to cooling.
It depends on the relative lapse rates of the environment and the air parcel being forced vertically
When does STABILITY exist?
When does INSTABILITY exist?
When the ELR is LESS than the SALR
When the ELR is greater than the DALR
What is CONDITIONAL stability?
When the ELR is LESS than the DALR but GREATER than the SALR
While a parcel of air remains dry and cooIs at the DALR, conditions will be STABLE. If
the parcel of air reaches dew point the parcel will cool at the slower SALR and if sufficient lifting occurs it will become warmer than the environment resulting in instability
What are the 4 types of inversions?
- Surface inversion
- air close to earths surface cooled at night my conduction - Turbulence inversion
- moderate low level winds may cause adiabatic expansion and cooling in lower layers due to expansion - Frontal inversion
- a cold front pushing warmer air above itself - Subsidence inversion
- if an air column subsides and falls and the air warms
What is the calculation for cloud height?
Surface Temp minus Dew Point ➗ 3 (DALR)
When a parcel of air becomes saturated and condensation occurs:
a. All the water vapour changes to liquid state
b. Latent heat is absorbed
c. Rain will commence
d. Latent heat is released
d. Latent heat is released
Relative humidity is:
a. The percentage degree of saturation
b. The ratio of the amount of water vapour to the amount of air in which it is contained
c. The ratio of the mass of water vapour to the mass of dry air in which it is held
d. Unaffected by changes in temperature
a. The percentage degree of saturation
The water vapour held in saturated air is:
a. Visible sometimes
b. Visible if the temperature is low enough
c. Visible always
d. Invisible always
d. Invisible always
If the ELR is between 1.5 and 3C the air is:
a. Stable
b. Unstable
c. Neutrally stable
d. Stable for dry air and unstable for saturated air
d. Stable for dry air and unstable for saturated air
Above the condensation level the lapse rate of rising air will:
a. Reduce from the dry adiabatic lapse rate to the smaller saturated adiabatic lapse rate
b. Increase from the saturated adiabatic lapse rate of the dry adiabatic lapse rate
c. Become isothermal
d. Undergo no change
a. Reduce from the dry adiabatic lapse rate to the smaller saturated adiabatic lapse rate
When the ELR is greater than the DALR, dry air is:
a. Stable
b. Unstable
c. Conditionally unstable
d. Conditionally stable
b. Unstable
When the SALR is greater than the ELR, saturated air is:
A. Stable
B. Unstable
C. Conditionally unstable
D. Conditionally stable
A. Stable
If the air is unstable, you can expect
A. Smooth flying conditions and unlimited vis
B. Smooth flying conditions and restricted vis
C. Bumpy flying conditions and unlimited vis
D. Bumpy flying conditions and restricted vis
C. Bumpy flying conditions and unlimited vis
