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PPL - Weather Patterns

Terms

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What is Adiabatic Heating and Adiabatic Cooling ?
Adiabatic Heating is when air descends it's pressure increases, volume decreases, and temp. increases.
Adiabatic Cooling is when air rises, pressure decreases, volume increases, and temperature decreases.
What is Temperature Inversion and when does it occur ?
-It is when temp. increases with alt.
-It occurs in stable air with little or no wind and turbulence.
What is Evaporation ?
It is when iquid water changes to invisible water vapor.
What is Condensation ?
It is when water vapor changes to a liquid, as when water drops form on a cool glass on a warm day.
What is Sublimation ?
It is when ice change into water vapor.
What is Deposition ?
It is when water vapor turns into ice.
What is Humidity and Relatvie Humidity ?
- Humidity simply refers to moisture in the air.
- Relative Humidity is the actual amount of moisture in the air compared to the total amount that could be present at that temperature.
When is air said to be saturated ?
When the dewpoint has been reached, as in when the air contains 100% of the moisture it can hold at that temp.
How do clouds form and how can you anticipate the formation of fog or cloud ?
As air cools to its saturation point, condensation changes invisible water vapor into clouds. By monitoring the differences between surface temp. and dewpoint. AKA temerpature/dewpoint spread.
What is the dry adiabatic lapse rate (unsaturated air) and the moist adiabatic lapse rate ?
- 3 degree celsius
(5.4 degree fahreneit)/ 1000 FT
- varies from 1.1 C to 2.8 degree C (2F - 5F)/1000 FT
Explain Atmospheric Stability ?
- In a stable enviroment, vertical airflow motions are smooth and small.
- In an unstable atmosphere, air rises because it is warmer than its surroundings (convection). This instability can lead to severe cloud development, turbulence, and hazardous weather.
How can air be cooled ?
By moving over a cooler surface, rising, or cooled from the underlying surface.
What do Stratus, Cumulus, Cirrus, and Nimbus all refer to ?
stratus > sheet-like clouds
Cumulus > puffy clouds
Cirrus > wispy clouds
Nimbus > violent rain
What are Low Cloud characteristics ?
- Low clouds extend from near the sfc. to about 6500 FT AGL.
- Consist of water, or supercooled water which can create an icing hazard for aircraft.
- Types include: stratus, stratocumulus, & nimbostratus
What are Middle Cloud characteristics ?
- Middle clouds have base ranage from about 6500-20000 FT AGL.
- Consist of water, ice crystals, or supercooled water, and may contain moderate turbulence and potentially severe icing.
- Types include: Altostratus and Altocumulus.
What are High Cloud characteristics ?
- High clouds have bases beginning above 20000 FT AGL.
- white to light gray in color and form in stable air.
- Consist of ice crystals and seldom pose a serious turbulence or icing hazard.
- Types include: Cirrus, Cirrostratus, & Cirrocumulus
The lifting of unstable air can cause...... ?
Vertical cloud development and turbulence.
What is an Airmass ?
is a large body of air with fairly uniform temp. and moisture content.
Describe the tropical airmass source regions ?
- from the south of west and east there is the
Martime Tropical (mT) [Warm,Moist]

- in the south is the
Continental Tropical (cT)
[Hot,Dry]
Describe the polar airmass source regions ?
- from the north of west and east there is the
Maritime Polar (mP)
[Cool,Moist]

- in the north is the
Continental Polar (cP)
[Cool,Dry]
What is a Front and wat is a Cold Front, Warm Front, Stationary Front, and Occluded front ?
Front: a boundary between airmasses
Cold front: cold air is moving to displace warmer air
Warm front: warm air is moving to displace colder air
Stationary front: has no movement
Occluded front: is when cold and warm fronts merge.
What is Frontal discontinuities and it's 3 types ?
- It is the rapid changes in the meteorological characteristics of an airmass

- Temperature, Wind, Pressure
What causes Radiation Fog ?
- moist air over low, flat areas on clear, calm nights.
What causes Advection Fog ?
- when a low layer, of warm , moist air moves over a cooler surface.
What causes Upslope Fog ?
- when moist, stable air is forced up a sloping land mass.
What causes Steam Fog ?
- when cold, dry air moves over comparatively warmer water.
Stratocumulus Clouds characteristics ?
- are white puffy clouds that form as stable air is lifted.
Nimbostratus cloud characteristics ?
- are gray or black clouds
- can be more than several thousand feet thick
- contain large amount of moisture
- produces widespread areas of rain or snow
- if temp. is below freezing, they may create heavy aircraft icing.

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