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EXPLAIN the term pressure gradient
- The rate of pressure change perpendicular to the isobars.
- The isobar spacing dictates the size of the pressure gradient force (PGF).
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EXPLAIN the term pressure gradient force
- The Initiating force for ALL winds
- High Pressure: Air descends downward and outward
- Low Pressure: Air moves inward and up.
- STRONG: isobars are close together
- WEAK: isobars are far apart
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EXPLAIN and identify gradient winds and Buys Ballot's Law with respect to the isobars around pressure systems in the Northern Hemisphere
- Caused by combination of Coriolis Force and Pressure Gradient Force
- Above 2000 AGL
- Winds move Parallel to Isobars (perpendicular to PGF)
- High Pressure: Clockwise
- Low Pressure: Counter Clockwise
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EXPLAIN and identify the surface wind direction with respect to the gradient winds in a pressure system in the Northern Hemisphere
- Surface Friction reduces the effects of the Coriolis Force
- Below 2000 AGL
- Causes 'Angled" winds
- Crossing Isobars
- High Pressure: Clockwise and out
- Low Pressure: Counter Clockwise and into
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DESCRIBE the jet stream
- Located just below tropopause, 30000MSL
- A narrow band of strong winds; 100-150kts and up to 250kts
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DESCRIBE sea breezes
- Daytime heating of the land.
- Air rises over land, cools off, and descends over water.
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DESCRIBE land breezes
- Created by land cooling off at night.
- Air flows over water, warms up, rises, then descends over land
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DESCRIBE mountain winds
Cools off at night and then descends down to the valley floor
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DESCRIBE valley winds
- Valley heated by the sun
- Warm air is displaced and forced up the mountain
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DEFINE saturation
- Saturation is the point at which air can hold no more water.
- Higher temp, more water vapor can be held
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DEFINE dew point temperature
Temperature at which saturation occurs
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DEFINE dew point depression
- the difference in Dew Point and actual Temperature
- aka Dew Point Spread
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DEFINE relative humidity
- The percent of saturation in the air.
- Dew Point Spread of 4° F or 90% RH = condensation into fog or clouds.
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DESCRIBE the relationship between air temperature and dew point temperature with respect to saturation
- Dew point swill ALWAYS be lower than the temperature.
- Dew point spread of 4° F or 90% RH = condensation into fog or clouds.
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DESCRIBE the relationship between air temperature and dew point temperature with respect to saturation
- Dew point swill ALWAYS be lower than the temperature.
- Dew point spread of 4° F or 90% RH = condensation into fog or clouds.
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DESCRIBE the three characteristics of precipitation
- Showers: Sudden beginning and ending. Abruptly changing intensity. Associated with cumuliform clouds
- Continuous: Steady. NOT showery. Intensity changes gradually. Associated with stratiform clouds
- Intermittent: Stops and starts at least one during the hour. Shower or steady. Associated with either cloud type
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DESCRIBE the types of precipitation
- Drizzle: freezing or liquid
- Rain: freezing or liquid
- Frozen: Hail, Ice Pellets, Snowmobile, or snow grains
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DESCRIBE the four principal cloud groups
- Low Clouds: Surface to 6500AGL
- Middle Clouds: 6500AGL to 20000AGL
- High Clouds: above 20000AGL
- Special Clouds: Extensive vertical development
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DESCRIBE the weather conditions associated with Low Clouds
- Surface to 6500 AGL
- Mainly composed of water droplets
- Icing accumulates faster on low clouds because they are more dense
- Can lead to terrain collision
- Turbulence: none to moderate
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DESCRIBE the weather conditions associated with Middle Clouds
- 6500 to 20000 AGL
- Mainly composed of ice crystals and water droplets (ALTO)
- Fog is often present, expect poor visibility
- Frequently dark and Turbulent
- Icing: common
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DESCRIBE the weather conditions associated with High Clouds
- Clouds above 20000 AGL
- Mainly composed of ice crystals (CIRRO)
- No Precipitation; no icing hazard
- Moderate turbulence with severe or extreme turbulence in anvil thunderstorms.
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DESCRIBE the weather conditions associated with Special Clouds
- Have extensive vertical development with high risk of Icing.
- Severe to extreme Turbulence, Hail, Icing, Lightning, and others.
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DESCRIBE the types of atmospheric stability
- Stable: Tendency to return to equilibrium
- Neutral Stable: Equilibrium encountered at any displacement
- Unstable: Tendency to move away from equilibrium
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DESCRIBE the four methods of lifting
- F - Frontal: Cold fronts lift air preceding it
- O - Orographic: Wind against a mountain side pushes the air up
- C - Convergence: Forces air up in between air masses
- T - Thermal: When cool air is over a warm surface, from solar heating
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DESCRIBE the flight conditions associated with a stable atmosphere
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DESCRIBE the flight conditions associated with a unstable atmosphere
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