Weather

Question 1

What is dry adiabatic lapse rate?
a. Moist adiabatic lapse rate?
b. The average lapse rate of the atmosphere?

Answer 1

Dry air tends to cool at a rate of 3 degrees C per 1000ft
a. Moist air tends to cool at a rate of 1.1-2.8 degrees C per 1000ft
b. 2 degrees C per 1000ft

Question 2

What are the three types of turbulence?

Answer 2

1) Convective - uneven heating of the Earth’s surface with little wind
2) Mechanical - caused by obstructions that disrupt smooth air flow (mountains, buildings, etc.)
3) Wind shear - Caused by wind currents of different directions/speeds

Question 3

What is the lowest altitude winds and temperature are listed on winds and temperature aloft forecasts?

Answer 3

Winds 1500ft AGL
Temperature 2500ft AGL

Question 4

What type of weather is included in a SIGMET?
a. A convective SIGMET?

Answer 4

• Severe or extreme turbulence or CAT not associated with a thunderstorm
• Severe icing not associated with a thunderstorm
• Widespread dust storm or sand storm lowering visibility to below 3 miles
• Volcanic ash

a. Severe thunderstorms due to:
- Surface winds greater than or equal to 50 knots
- Hail at the surface greater than or equal to 3/4 of an inch
- Tornadoes
- Embedded thunderstorms
- Line of thunderstorms
- Thunderstorms producing greater than or equal to heavy precipitation affecting 40% or more of an area of at least 3000 square miles

Question 5

What is a Center Weather Advisory?

Answer 5

An unscheduled in-flight weather advisory used to supplement AIRMETs, SIGMETs, convective SIGMETs

Question 6

Define the following:
- Evaporation
- Sublimination
- Condensation
- Deposition

Answer 6

• Evaporation - From liquid to gas
• Sublimination - From solid to gas
• Condensation - From gas to liquid
• Deposition - From gas to solid

Question 7

Describe the different types of clouds.
a. What altitudes define low, middle, and high clouds?

Answer 7

• Cumulus - puffy cottonball-like. Bases are usually low to middle clouds, but tops can rise as high as FL600
• Stratus - layered clouds, usually low level
• Nimbus - rain clouds
• Cirrus - thin, wispy, high level clouds usually composed of ice crystals
• Castellanus - common bases, but separate vertical development
• Lenticular - lens-shaped that form over mountains in high wind
• Fracto - ragged or broken clouds
• Alto - middle level clouds between 5000-20000ft

a. Low - surface to 6500ft AGL
Middle - 6500 to 20000ft AGL
High - above 20000ft AGL

Question 8

What are some examples of mechanisms that can cause a lifting action?

Answer 8

• Orographic effects - winds moving across mountains and valleys
• Frictional effects - low pressure systems
• Frontal lifting
• Buoyancy - uneven heating of the surface
• Converging winds
• Drylines
• Outflow boundaries generated by prior storms
• Local winds - land breeze, sea breeze, lake breeze, valley breeze

Question 9

What are the 3 kinds of thunderstorms?

Answer 9

• Single cell (AKA airmass)
• Multi-cell (AKA steady state) - cluster of cells in various stages of the thunderstorm
• Super-cell - especially dangerous storm usually consisting of a single cell that can persist for an extended period

Question 10

How does dew form?
a. How does frost form?

Answer 10

Dew forms when a surface cools below the dewpoint, causing water vapor to condense.
a. Frost forms when the surface is colder than the dewpoint and the freezing level