Weather Clouds And Fog Flashcards
Stable air masses
• A stable air mass makes vertical development difficult.
Unstable air masses
• An unstable air mass has turbulent air and convective activity.
Laps rate
the rate at which an air mass cools as it is lifted.
Sublimation
Sublimation: transition of a substance from solid to gas (without liquid phase). Adds or removes moisture in air.
Evaporation
Evaporation: transition from liquid to vapor. Adds moisture to air.
Condensation
Condensation: transition from vapor to liquid. Removes moisture from air.
Adiabatic
Adiabatic: the process by which an air mass cools as it is raised into the atmosphere.
Jet stream
Jet Stream
• A jet stream is when the wind is more than 50 knots.
• It can reach up to 240 knots and is typically 4 to 8 miles in height.
• They are located around the globe at different altitude and latitude.
• It moves North and is weaker in the summer,
• It moves South and is stronger in the winter.
Clear turbulence
It moves South and is stronger in the winter.
Clear Air Turbulence
• Sudden severe turbulence occurring in cloudless regions that causes violent buffeting of aircraft.
• Encountered above 15,000 AGL and not associated with clouds or thunderstorms.
• Commonly applied to higher altitude turbulence with wind shear.
• Identified through long streaks of cirrus clouds.
• Greatest turbulence occurs with a curved jet stream associated with a deep low pressure trough.
• Expect strong wind shear in the jet stream front above a core with a speed of 60 to 90 kts.
Fronts
Fronts
• As an air mass moves across bodies of water and land, it eventually comes in contact with another air mass with different characteristics.
• Change in temperature occurs when flying across a front.
• Wind direction also changes when flying across a front.
• Squall line is a narrow band of thunderstorms. Usually forms with a cold front.
Fronts
Temperature/dewpoints
Temperature/Dew Point
• The dew point is the temperature at which air must be chilled to become saturated.
• Dew point is reported in several weather reports, including the ATIS and on the AWOS/ASOS frequency.
• Close dew point and temperature, the more likely it is that visible moisture will be present (fog, dew, frost, clouds, rain, or snow).
Convecting currents
Convective Currents
Convective currents are influenced by the type of surface:
Rocks, sand, barren land, concrete (parking lots) give off large amount of
heat.
v Water, trees, and other vegetation tend to slowly absorb heat.
Low level wind shear
Low Level Wind Shear
• Sudden, drastic change in wind speed and/or direction over a very small area.
• Occur at any altitude but dangerous when occurring at low altitude.
• Associated with passing frontal systems, thunderstorms, temperature inversions and strong upper level winds.
• Microbursts are a form of LLWS. They can last 5-15 minutes, create downdraft up to 6000 feet/min, and wind changes of 30-90 knots!
Low level wind shear
Low Level Wind Shear
• Sudden, drastic change in wind speed and/or direction over a very small area.
• Occur at any altitude but dangerous when occurring at low altitude.
• Associated with passing frontal systems, thunderstorms, temperature inversions and strong upper level winds.
• Microbursts are a form of LLWS. They can last 5-15 minutes, create downdraft up to 6000 feet/min, and wind changes of 30-90 knots!
Fog
Fog
• Fog is a cloud that is on the surface.
• Occurs when an air mass close to the ground is cooled to the dew point.
• Classified according to the manner in which it forms.
Radiation Fog
/ Advection Fog
v Upslope Fog v Steam Fog
Radiation Fog
