Clouds Flashcards
How are clouds formed?
the lowering of temperature to the dew (or frost) point to cool it to its saturation level
What are the two processes by which temperature can be lowered to its dew point
- Diabatic processes: Involves the removal or input of heat
- Adiabatic processes: Does not involve the removal or input of heat
What is the dew point?
A temperature that, when reached, condenses water vapour into a droplet
Describe the diabatic process
When energy is added to or removed from a system
- heat transfer is usually from higher to lower temperatures
- usually involved in large-scale air movements (moving warm air from the equator to the poles)
Describe abiabatic process
changes the temperature without adding or removing heat from a parcel of air
- this happens because air expansion removes heat, and air compression adds heat
What is the adiabatic lapse rate?
The rate at which a rising parcel of unsaturated air cools
How much does the air cool by elevation?
For every 100m in elevation, the temperature cools by -1 degrees
What is the lifting condensation level
The temperature of the air parcel of rising air has lowered to the dew point (so condensation commences)
- Once condensation occurs, the air parcel warms more than the surrounding area, so air cools by rising and warms after condensation.
What are the four mechanisms that lift air so that condensation and cloud formation can occur?
- Orographic uplift
- Frontal uplift
- Convergence
- Convection
Describe orographic uplift
The upward displacement of air that leads to adiabatic cooling
- orographic means mountain
- on the downwind side of the mountain ridge, air descends the slope and warms by compression to create a rain shadow effect
Describe frontal uplift
Airflow along frontal boundaries results in the development of clouds by:
- Cold air advances toward warmer air (cold front), and the denser cold air displaces the lighter warm air ahead.
- warm air flows toward the cold air (warm front), the warm air is forced upward
Describe convergence uplift
When a low-pressure cell is near the surface, winds in the lower atmosphere tend to converge towards it, and the air has nowhere to go but up.
Describe convection uplift
Localized convective lifting due to buoyancy; heating the air near the surface forces air up by convection.
What does the buoyancy of a rising air parcel depend on?
Its rate of cooling relative to the surrounding air is rising to
List and describe the three stability characteristics of air
- Unstable air is buoyant and continues to rise after an initial uplift
- Stable air resists uplift and sinks back to its initial position after an initial push
- Conditionally unstable air will rise or fall, depending upon the condition of condensation within the parcel of air.
Level of free convection
The height to which a parcel of air must be lifted for it to become buoyant and rise on its own
What influences the surrounding air temperatures?
- Heating/cooling of the lower atmosphere
- Advection of cold and warm air at different levels.
- Advection of air masses with different rates of cooling.
How does rising air stop rising?
it encounters a region of stable air caused by temperature inversions, undergoing entrainment
Entrainment
A mixing of ambient air into another parcel due to turbulence. Entrainment prevents cloud formation by adding unsaturated air into a saturated parcel
temperature inversion
extremely stable and resist vertical mixing
stratus
layered (blanket like clouds)
cumulus
round and puffy
low elevation clouds (based below 2 km) are clouds made up of ______?
water droplets
stratocumulus
Aggregated group of cumulus clouds
