Atmospheric Stability Flashcards
Explain how atmospheric stability is determined.
- Adiabatic = air cools when it rises/expands and warms when it descends/contracts
- Does not transfer heat in or out of the parcel of air
- Air rises at either the dry adiabatic lapse rate (3/100ft)
OR - Air rises at the saturated adiabatic lapse rate (1.5/1000ft)
What is air at the DALR?
Unsaturated
What happens at the SALR?
Cloud will form
What is the Environmental Lapse Rate (ELR)?
Air surrounding the rising air.
When is air unstable?
- If surrounding air colder than SALR and DALR.
- Because warmer air wants to rise
- Stable if surrounding air warmer than SALR and DALR
What happens if ELR is between SALR and DALR?
- Air is conditionally unstable.
Describe the typical diurnal variation of stability.
- Diurnal stability linked to temperature
- Increase temperature = increase instability
- Maximum instability = mid afternoon
- Decrease temperature below 0degrees=32 Fahrenheit increase stability (max sunrise)
Explain why the SALR steepens with increasing height and increasing latitude.
- Water vapour becomes cloud when it reaches dew point.
- Increasing altitude = reduced water vapour due rain/cloud
- Increasing latitude = reduced water vapour
- Reduced water vapour means less latent heat released
ELR of 1/1000ft
Atmosphere is ABSOLUTELY STABLE
ELR of 4/1000ft
Atmosphere is ABSOLUTELY UNSTABLE
ELR is 2/1000ft
Atmosphere is CONDITIONALLY STABLE/UNSTABLE
ELR between 1.5 and 3
Atmosphere = CONDITIONALLY STABLE/UNSTABLE
ELR is greater than DALR
Atmosphere = UNSTABLE IN ALL CIRCUMSTANCES
ELR = DALR
Atmosphere = NEUTRAL IF UNSATURATED, UNSTABLE IF SATURATED
ELR is less than DALR but is less than SALR
Atmosphere = stable if unsaturated, unstable if saturated.
ELR = SALR
Atmosphere = STABLE IF UNSATURATED, UNSTABLE IF SATURATED
ELR is greater than SALR
Atmosphere = STABLE IN ALL CIRCUMSTANCES
ELR is negative
Atmosphere = STABLE IN ALL CIRCUMSTANCES
