Weather Flashcards
What is the atmosphere?
The atmosphere is a mixture of gases that surrounds the earth. It provides us with air to breathe, it acts as a shield to protect us from the sun’s UV rays, it regulates the earth’s temperature, etc.
How is the atmosphere composed?
The atmosphere is composed of several gases but mostly nitrogen and oxygen.
Nitrogen 78%
Oxygen 21%
Trace gases 1%
What happens to the warm air and cold air in the atmosphere in relation to it’s motion?
Hot air rises and cool air takes over.
What is the Coriolis effect?
The Coriolis effect is the phenomenon that causes fluids like water or air to curve as they travel across or above the Earth’s surface.
How do High and Low pressure areas act in the Northern Hemisphere?
In the northern hemisphere the high pressure areas rotate clockwise as it sinks and the low pressure areas rotate counterclockwise as it rises.
How are high pressure and low pressure areas associated?
High pressure areas are areas of cold dry descending air in a clockwise rotation direction with the following characteristics:
- Light winds
- Good weather
- Stable air
- Clear skies
Low pressure areas are areas of hot rising air in a cyclone rotation direction with the following characteristics:
- Cloudy skies
- Unstable air
- Precipitation
- Strong winds
What is a front?
A front is a boundary where two different air masses meet. These air masses have different temperatures and humidity levels. When they come together, they can cause changes in the weather, such as rain, clouds, or changes in temperature.
What are the 4 types of fronts?
- Cold front
- Warm front
- Stationary front
- Occluded front
Explain a warm front
A warm front occurs when a warm air mass advances and replaces a colder air mass, covering the cold air mass from the top and forcing it out and below. This type of front moves relatively slowly, about 10-15 mph.
The characteristics and type of clouds a warm front brings are:
- Cirrus clouds and stratiform clouds
- Steady precipitation
- Pressure falls steadily ahead of the front and stabilizes or rises slightly once it passes.
- Poor visibility due to haze or fog
Explain a cold front
Cold fronts occur when a cold air mass advances and pushes under a warmer air mass forcing the warm air mass to rise. During cold fronts it is very common to expect precipitation, cloudy skies and often thunderstorms. Cold fronts move faster than warm fronts, typically about 25-30 mph.
The characteristics and type of clouds a cold front brings are:
- Cumulonimbus clouds and towering cumulous
- Poor visibility during the passage and good visibility after
- Gusty winds
- Rising atmospheric pressure
Explain stationary fronts
A stationary front occurs when two air masses, one warm and one cold, meet but neither is strong enough to replace the other. This results in the front remaining in place for an extended period. Stationary fronts often bring prolonged and steady precipitation that could last for hours or days.
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Stationary fronts have weather characteristics from both cold and warm front, including poor visibility and prolonged precipitation.
Explain occluded fronts
An occluded front occurs when a cold front catches up with a warm front, lifting the warm air mass off the ground being trapped between two cooler air masses.
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There are two types of occluded front:
- Warm occlusion
- Cold occlusion
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The type of weather depends if its a warm occlusion or a cold occlusion but typically steady precipitation, statiform clouds and if the atmosphere is unstable there is a high change of thunderstorms.
What is a squall line?
A squall line is a line of thunderstorms that form ahead of a cold front.
What is dewpoint?
The dew point is the temperature at which the air becomes saturated.
What is pressure altitude?
Pressure altitude is true altitude corrected for non standard pressure.
What is density altitude?
Density altitude is pressure altitude corrected for non standard temperature.
What is fog?
Fog is a low level cloud of tiny water droplets suspended in the air near the ground. It’s the result of the air near the surface to cool to it’s dewpoint and condense.
When does fog usually form?
Fog forms when air near the surface cools to it’s dew point, which causes water vapor to condense.
What are the different types of fog?
- Upslope fog
- Steam fog
- Precipitation fog
- Advection fog
- Ice fog
- Radiation fog
What are some weather phenomenons that occur when air becomes saturated?
- Dew
- Frost
- Fog
- Clouds
- Rain
- Snow
What is a thunderstorm and what are the three ingredients of a thunderstorm?
A thunderstorm is a weather event that involves lightning, thunder, heavy rain, and often strong winds. The three ingredients of a thunderstorm are:
- Lifting action
- Unstable atmosphere
- Moisture
How do thunderstorms create?
Thunderstorms forms when warm moist air rises in an unstable
atmosphere. As the warm air rises, it cools and the moisture in it condenses into water droplets, creating clouds. As more warm moist air rises, the cloud grows vertically turning into a cumulonimbus cloud. Inside the cumulonimbus cloud all air, water and ice particles bum into each other creating electric charges.
What is windshear?
Wind shear is a sudden change in wind speed and direction over a short distance, it can occur either horizontally or vertically.
What is turbulence?
Turbulence is a sudden change in air flow that causes the airplane to change it’s attitude, altitude and direction.
What are four different types of turbulence?
- Thermal turbulence
- Wake turbulence
- Mechanical turbulence
- Clear turbulence
What are the three types of aircraft structural icing?
- Clear Ice
- Rime Ice
- Mixed Ice
Explain clear ice
Clear ice happens when supercooled water dropplets freeze slowly upon contact with the aicraft’s surface, creating a clear layer of ice.
Explain rime ice
Rime ice forms when supercooled water droplets freeze rapidly upon contact with the aircraft, creating a rough, white, and opaque layer of ice.
Explain mixed ice
Mixed ice is a combination of clear and rime ice, resulting from varying cloud conditions with both large and small supercooled water droplets.
How much does air pressure decrease with altitude?
Air pressure decreases with altitude by approximately 1 inch per 1,000ft
How is the airplane performance affected with high density altitude?
High density altitude, which occurs when the air is less dense due to high elevation or high temperatures, can significantly affect aircraft performance by a reduced engine performance due to the reduced amount of air molecules, reduced lift generated by the wings due to the less air available, longer takeoff and landing distances.
What are the phases of matter?
What causes air movement?
Air movement in the atmosphere is primarily caused by differences in air pressure, which result from uneven heating of the Earth’s surface.
- Air movement results from unequal heating of the earth’s surface.
- Air moves from high pressure to low pressure, warm air is less dense so it rises and cold air is more dense so it sinks.
- Air movement bends due to Coriolis Effect.
- Air movement slows at the earth’s surface due to friction.
When do clouds appear?
Clouds appear when moist air rises, cools, and reaches its dew point, causing the water vapor to condense into tiny water droplets or ice crystals.
How are clouds classified and what are the types of clouds?
What are lenticular clouds?
Lenticular clouds are lens-shaped clouds that form over mountainous or hilly terrain. This are created by air flowing over mountains or ridges, causing the air to rise and create a stationary wave pattern. They are often associated with strong turbulence and updrafts or downdrafts in the vicinity.
What are isobars?
Isobars are lines drawn on weather maps that connect points with the same air pressure. When isobars are close together, strong wings can be expected.
What is frost?
Frost is the formation of ice crystals on surfaces when the temperature falls below the freezing point of water causing moisture to condense and freeze.
What are the three stages of a thunderstorm?
- Cumulus stage
- Mature stage
- Dissipating stage
Explain the cumulus stage of a thunderstorm
This the initial stage of a thunderstorm. It begins with the development of cumulus clouds, which form as warm, moist air that rises and cools. Updrafts cause the cloud to grow vertically. At this stage, the storm is relatively calm with light precipitation.
Explain the mature stage of a thunderstorm
In this stage, the thunderstorm is fully developed. The cloud reaches its peak height, forming a cumulonimbus cloud. This stage is characterized by strong updrafts and downdrafts, heavy rainfall, thunder, lightning, and possibly hail.
What is hail?
Hail is a type of precipitation consisting of solid ice that forms inside thunderstorm updrafts and falls to the surface as ice balls.
How does hail form?
Hailstones are formed when raindrops are carried upward by thunderstorm updrafts into extremely cold areas of the atmosphere and freeze. Hailstones then grow by colliding with liquid water drops that freeze onto the hailstone’s surface.
What are microburst?
A microburst is a localized, intense downdraft within a thunderstorm that causes a sudden, powerful outflow of air to spread out horizontally when it hits the ground. They typically last about 5-15 minutes.
When can windshear be expected in a cold front?
In cold fronts critical wind shear happens after
When can windshear be expected in a warm front?
In warm front critical wind shear happens before
What are some characteristics of stable and unstable air?
What is a METAR and how often does it update?
METAR is a standardized weather report that provides essential information about current weather conditions at an airport. This report provides information like temperature and dew point, wind, visibility, weather conditions, cloud cover, barometric pressure and density altitude. It usually updates every hour or every significant change in weather.
What is a TAF and how often is it updated?
A TAF (Terminal Aerodrome Forecast) is a weather forecast specifically for the area around an airport. TAFs offer forecasts of expected weather including wind, visibility and significant weather.
What is a SPECI?
A SPECI is a special weather report issued when significant or sudden major changes in weather occur between regular METAR that are concerning for the safety of the flight.
How will frost on the wings of an airplane affect takeoff performance?
Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability.
What is a Convective SIGMET?
A Convective SIGMET is an advisory for pilots that warns about sever convective activity. Convective SIGMET covers dangerous lines of thunderstorms, heavy rain which affects at least 40% of the SIGMET zone, tornadoes, hail of at least ¾ of an inch, as well as wind shear.
How long are AIRMETS and SIGMETS valid for?
AIRMETS are typically valid for 6 hours.
SIGMETS are typically valid for 4 hours.
CONVECTIVE SIGMETS are typically valid for 2 hours (Issued at 55 minutes past the hour)
What other information besides weather does the ATIS provide?
The ATIS provides other information like NOTAMS, runway closures, approaches, etc.
Does the AWOS or ASOS provide any airport information as the ATIS?
No, ASOS and AWOS only provide weather information.
What is AWOS?
AWOS is an automated system that measures and broadcasts current weather data.
How often do AWOS reports update?
AWOS reports report every minute.
What is ASOS?
Automated Surface Observing System (ASOS) is an automated system that provides information about weather, it is more advanced than AWOS and updates typically every minute.
How precise does the AWOS report wind direction?
AWOS records wind direction with a typical precision of 10 degrees
How far should we stay away from a thunderstorm?
At least 20 miles
What problems can a pilot encounter in thunderstorms?
In thunderstorms pilots can face several dangers like turbulence, hail, lightning, windshear, heavy rain.
Where can you find ATIS, AWOS, ASOS frequencies?
- A/F Directory
- Sectional charts
- Approach plates
- FAA directory
What is the temperature/ dew point spread?
Temperature/ Dew point spread is the difference between the air temperature and the dew point temperature.
What are the air lifting actions?
- Convection: Warm air rises due to heating.
- Orographic Lift: Air rises over mountains.
- Frontal Lift: Warm air rises over colder air at fronts.
- Convergence: Air from different directions comes together and rises.
- Mechanical Lift: Air is forced upwards by obstacles.
Explain radiation fog
Radiation fog forms typically on clear calm nights when the ground cools due to radiation causing the air above it to cool, if there is enough moisture, the air condenses and fog forms.
Explain upslope fog
Upslope fog forms when warm moist air is forced up a mountain, it cools and the water vapor condenses into fog.
Explain steam fog
Steam fog forms when cold dry air moves over warm water, warm water evaporates and moisture in the air turns into fog as it cools.
Explain advection fog
Advection fog forms when warm, moist air moves over a cooler surface, causing the air to cool and the moisture to condense into fog.
Explain ice fog
Ice fog forms when moisture in the air freezes into tiny ice crystals.
Explain precipitation fog
Precipitation fog forms when rain falls into cooler air near the ground. The rain evaporates, adding moisture to the air, which then cools and condenses into fog.
How often are TAFs and METARs updated?
TAFs are usually issued four times a day, every six hours, at set times: 0000Z, 0600Z, 1200Z, and 1800Z (Zulu time).
but they can also update on significant changes.
