Formation of clouds and Weather Flashcards
explain 5 reasons why clouds are important in meteorology in relation to: Forms of weather Precip formation Effects on heat budget Atmospheric processes: Actual conditions
Forms of weather: their presence counts as one
Precip formation: its formed in clouds
Effects on heat budget: absorbs and reflects radiation
Atmospheric processes: provide clues to which processes are taking place
Actual conditions: can provide visual clue to amount of moisture, as well as probability for turbulence and icing
what are the 2 main processes in the atmosphere that produce cloud:
Cooling
Evaporation
what are the 2 main types of cooling
Adibatic cooling
Diabatic cooling
Define the diabatic process:
The process in which there is an exchange or transfer of heat across the boundaries of a parcel.
List the 3 common types of diabatic cooling
Radiation
Advection
Mixing
what are the 2 examples of radiative cooling leading to the formation or modification of cloud?
- Radiation cooling at the surface, through conduction, can lead to fog or stratus
- Radiation cooling aloft may cause cloud to form or develop in the vertical
If vertical mixing is sufficient, radiation fog may become thick enough to produce:
Total sky obscuration.
The main difference between radiation fog and radiation stratus is:
Based on the wind speed. Light wind favors fog where moderate winds will lead to stratus
explain how radiative cooling aloft affects stability and may lead to vertical cumuliform clouds:
Radiation cooling from the top of the cloud, combined with the greenhouse effect below cloud will lead to instability and vertical development clouds embedded in an SC or AC layer (ACC and TCU).
Describe advection diabatic cooling
WAA is combined with conduction. warm moist air physically moves over a colder surface and loses heat to it. advection fog forms if the air is cooled to its dew point.
Coastal stratus forms when:
Warm air moves across progressively colder water.
Why will the onshore flow not produce stratus over land during the day?
Surface heating counteracts any inland penetration. It may form inland at night due to radiation cooling
Explain Diabatic cooling via mixing:
Warm moist air may lose heat by mixing with the colder air. If the final temperature of the mixed air is below the dew point, Cloud will develop
Clouds may form as a result of turbulent mixing. Explain:
When wind blows, turbulent eddies are created. These eddies result in cold air aloft warming as it is carried down, and warm air at the surface cooling as it is carried aloft. If moisture is high enough, air will become saturated at the top of the mixing layer and SC or ST will form.
Describe the adiabatic process:
There is no heat exchange across the boundaries of a parcel and heating or cooling of the parcel occurs through compression or expansion of the parcel due to pressure change.
If we lift a parcel of moist air into the atmosphere, it undergoes a decrease in
Density due to expansion.
Large scale upward vertical velocity results from a combination of:
Low level convergence and upper level divergence
List the 5 synoptic situations where large scale dynamic lift will often produce clouds and Wx JUVWR
- Vicinity of low pressure centers and troughs
- Regions of baroclinic development
- in advance of Warm front and TROWALS (Max WAA)
- ahead of Upper short wave troughs (PVA)
- Jet stream maximums (RELE)
state the main cause of cloud formation in the boundary layer:
Low level convergence generating upward vertical motion.
The procedure for assessment of boundary layer clouds, precipitation and restrictions to visibility requires the use of:
a current analysis and a short range surface prognosis.
List the 6 broad scale processes used to assess the presence of boundary layer clouds and precipitation: LUSLEC
- Low level convergence
- Upslope/Onshore flow
- Surface winds (>15 knots)
- Large area with moist surface conditions
- Evaporation or precipitation
- Cooling by advection/conduction
The 2 factors of primary importance in regards to diurnal variations are:
Temperature and Humidity
A flow of air moving over an increasingly higher ground elevation will be lifted:
Adiabatically.
Explain how boundary layer clouds are lowered in precipitation
Precip causes an increase in moisture due to evaporation. evaporation cools the air due to latent heat storage resulting in lower temperatures. Lower temp + greater moisture = lower ceiling.
