Meterology Flashcards
States of matter
Solid
Liquid
Gas
6 changes of state are
MDS FEC
MELTING
DEPOSITION
SUBLIMATION
FREEZING
EVAPORATION
CONDENSATION
Melting
When a solid becomes a liquid
Evaporation
When a liquid changes to a gas,
(heat energy is absorbed by the liquid)
Condensation
When a gas becomes a liquid
(gives up heat)
Freezing
Liquid changes to a solid
(When cools gives up heat)
Deposition
When gas becomes a solid
(releases, energy/heat)
Sublimation
When a solid becomes a gas
(Absorbs energy/heat) Ie. dry ice
Dew point
The temperature that air must be cool to in order to reach 100% saturation
Relative humidity
The ratio of the actual water vapour present in the air to the amount which the same volume of air would hold if it were saturated at the same atmospheric pressure and temperature
When do clouds form?
When warm air rises, as it rises, it will expand and cool.
Environmental lapse rate
The measured decrease in temperature with height above the ground. It is actually observed not a theoretical one.
Adiabatic process
The heating or cooling of the atmosphere without adding or subtracting heat
Dry adiabatic, lapse rate
DALR
3°C per 1000 feet of altitude. Use this calculations of temperature at altitude for dry air.
What is the decrease in dewpoint temperature?
0.5°C per 1000 feet.
Calculating cloudbase height equation
1000 x (temp-dew point) / 2.5= cloud base height 
Calculation of temperature at altitude in unsaturated air:
1.5°C per 1000 feet of increase in altitude.
When does Precipitation occur?
When water droplets, gross, efficiently in size and weight to overcome lifting agents, such as fronts and up drafts
Three types of rainfall
1 Convergent and cyclonic,
2 Orographic or relief
3 convectional
Convergent and cyclonic rainfall:
Caused by the convergence of two air masses or Fronts
Warm front rainfall =steady
Cold front rainfall =showery
Orographic or relief rainfall
When warm, moist air is forced to rise over an obstacle mountain range it cools
Convectional rainfall
When ground surface is locally heated, and the adjacent air expands and rises
When does snow form?
Under the same conditions as rain, except that the dewpoint temperatures are below freezing, so the vapour condenses straight to a solid (deposition)
How to determine base of cull is clouds (FGU)
Determine the spread between temperature and dewpoint, and multiplied by 400
Stable air
A small changes resisted and stable. System returns to its previous state.
Unstable air
A small change, initiate a bigger change, leading to one bigger, still…
Dry adiabatic, lapse rate
DALR
A balloon rising (air parcel) will cool at 3°C per 1000 feet
Saturated adiabatic lapse rate
SALR
A balloon rising (air parcel) will cool at 1.5°C per 1000 feet.
Stable air will be:
Smooth flying
Poor visibility
Steady precipitation
Layer cloud (stratus)
Ultimate – fog
Shallow lapse rate
Inversion
Warm air moving over cold air
Unstable air will be:
Bumpy flying
Good visibility
Showery precipitation
Cumulus clouds (heap)
Ultimate – thunderstorm
Steep lapse rate
High temperature/do point spread
Lapse rate in atmospheric stability
Steep lapse rate
Shallow lapse rate
Inversion
Isothermal layer
Ways to cause surface heating
Radiation – reflection of the earths rays
Conduction – warm air, contacting cold air
Advection – horizontal movement of air
Convection - unequal surface heating
Lifting processes
convection:
This happens due to unequal surface heating
Lift processes
Convergence:
Excess air rises as pressure systems meet
Lifting processes,
mechanical disturbance:
Surface friction
Lifting processes
Orographic lift:
Air moving up hills/mountains (anabatic)
Lifting processes,
frontal lift:
Advancing air being pushed up by cold air on the bottom
What is a cloud?
Visible aggregate of tiny water, droplets, and/or ice crystals that are suspended in the atmosphere
SKC
Clear sky
FEW
1/8 to 2/8 of the sky covered
SCT
Scattered 3/8 to 4/8 of the sky covered
BKN
Broken 5/8 to less than 8/8 of the sky covered
OVC
Overcast, 8/8 covered
When is there a ceiling?
Whenever the sky is either broken BKN or overcast OVC
Clouds are classified into for families
High clouds
Middle clouds
Low clouds
Clouds with vertical development
Hi clouds are:
Cirrostratus (CS)
Cirrocumulus (CC)
Cirrus (CI)
20,000-40,000ft
Middle clouds are:
Altostratus (AS)
Altocumulus (AC)
Altocumulus Castellanus (ACC)
Low clouds are:
Stratus (ST)
Stratocumulus (SC)
Nimbostratus (NS)
Stratus Fractus (SF)
Cumulus Fractus (CF)
(Found at altitudes between the surface to 6500 feet)
Clouds with vertical development are:
Cumulus (CU)
Towering cumulus (TCU)
Cumulonimbus (CB)
Alto, cumulus, Castellanus (ACC)
Cirrus clouds:
High and wispy typically found at heights greater than 20,000 feet, a current high pressure systems. They point in the direction of air movement mainly composed of ice crystals.
Cirrostratus
Sheet like high-level clouds, composed of ice crystals. Somewhat rare characterized by high ice crystals.
Altocumulus (AC)
These are puffy, cotton ball type clouds. On a warm and humid summer morning they may be followed by a thunderstorm.
Stratus (ST)
Low layer cloud. Smooth air. Resembles fog, but does not rest on the ground.
Altostratus (AS)
Layer cloud with no definite pattern, stele, or bluish in color. Sometimes the sun or moon can be seen dimly through.
Altocumulus, Castellanus (ACC)
Created from instability associated with air flows, having Mark vertical, sheer and weak thermal stratification.
Stratus (ST)
No, for a drizzle or freezing drizzle updrafts associated with stratus clouds are very weak.
Nimbostratus (NS)
Dark, low level, clouds, often accompanied by steady, light to moderate continuous precipitation.
Stratocumulus (SC)
Low lumpy layer of clouds. Sometimes accompanied by weak intensity precipitation.
Stratus Fractus (SF)
Stratus cloud that has been torn by wind into fragments. Drizzle may fall from these clouds.
Cumulus (CU)
Appearance of floating cotton or popcorn, popping, and have a lifetime of 5 to 40 minutes.
MUST KNOW:
Indicates the presence of significant vertical currents at low levels without precipitation.
Cumulus (CU)
Towering cumulus (TCU)
Growing cumulus cloud. On the way to becoming a cumulonimbus.
Cumulonimbus (CB)
Thunder and lightning are associated with. Fuelled by vigourous convective updrafts that at times are in excess of 50 kn and contain the greatest turbulence.
The suffix “Nimbus”
means:
Precipitation
Like the prefix “nimbo”
Mammatus
Powerful cumulonimbus clouds may have appendages protruding from the base of them called Mammatus clouds
Orographic clouds
Developed when air is forced to rise by the Earth topography (mountains)
Lenticular clouds
Forms in the wave crest, very high and hundreds of miles long
Rotor clouds
Associated with mountain wave activity
Cap clouds
Lies over the top of the mountain, and extends partially down the leeward slopes, indicating an extremely strong downdraft
Contrails
A cloud that is formed by the water vapour contained in the exhaust of jet engines. At high enough altitudes, the cold temperatures will instantly turn the vapour into ice crystals.
Roll cloud
Associated with thunderstorms. Exercise, extreme caution around roll clouds!
