Nature of the Atmosphere (part 1) Flashcards

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1
Q

State the general characteristics in regard to the direction of air around high and low pressure systems in the Northern Hemisphere. (AC00-6)

A
  1. Low pressure: counterclockwise
  2. High pressure: clockwise
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2
Q

If your route of flight takes you towards a low-pressure system, in general, what kind of weather can you expect? What if you were flying towards a high-pressure system? (AC 00-6)

A
  1. A low-pressure system moves inward and upward, and is conducive to cloudiness, precipitation and bad weather
  2. A high-pressure system moves outward and downward, and tends to favor dissipation of cloudiness and good weather
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3
Q

Describe the different types of fronts. (AC 00-6)

A
  1. Cold front—Occurs when a mass of cold, dense, and stable air advances and replaces a body of warmer air
  2. Warm front—The boundary area formed when a warm air mass flows over a colder air mass
  3. Occluded front—A frontal occlusion occurs when a fast-moving cold front catches up with a slow-moving warm front. Two types: cold front occlusion and warm front occlusion
  4. Stationery front—When the forces of two air masses are relatively equal, the boundary that separates them remains stationary
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4
Q

What are the general characteristics of the weather a pilot would encounter when operating near a cold front? (FAA-H-8083-25)

A
  1. Towering cumulus or cumulonimbus clouds
  2. Heavy rain accompanied by lightning, thunder and/or hail
  3. Tornadoes possible with winds variable and gusting
  4. Temperature/dew point and barometric pressure drop rapidly
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5
Q

What are the general characteristics of the weather a pilot would encounter when operating near a warm front? (FAA-H-8083-25)

A
  1. Stratiform clouds with possible rain and/or drizzle
  2. Low ceilings and poor visibility
  3. Variable winds
  4. Rise in temperature
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6
Q

What is a trough? (AC00-6)

A
  1. A trough line is an elongated area of relatively low atmospheric pressure
  2. At the surface when air converges into a low, it cannot go outward against the pressure gradient, nor can it go downward into the ground; therefore, a trough or a low, is an area of rising air
  3. Rising air is conducive to cloudiness and precipitation; hence the general association of low pressure and bad weather
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7
Q

What is a ridge? (AC00-6)

A
  1. A ridge (also called a ridge line) is an elongated area of relatively high atmospheric pressure
  2. Air moving out of a ridge or a high, flows downward; therefore, these are areas of descending air
  3. Descending air favors dissipation of cloudiness; hence the association of high pressure and good weather
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8
Q

What are the standard temperature and pressure values for sea level? (AC00-6)

A
  1. 59°F or 15°C
  2. 29.92” Hg
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9
Q

What are isobars? (AC00-6)

A
  1. An isobar is a line on a weather chart which connects areas of equal or constant barometric pressure
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10
Q

If the isobars are relatively close together on a surface weather chart or a constant pressure chart, what information will this provide? (AC00-6)

A
  1. How steep or shallow a pressure gradient is
  2. When isobars are spaced very close together, a steep pressure gradient exists which indicates higher wind speeds
  3. A shallow pressure gradient (isobars not close together) usually means wind speeds will be less
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11
Q

What is the name of the force that deflects winds to the right in the northern hemisphere and left in the southern hemisphere? (AC00-6)

A
  1. The Coriolis force
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12
Q

Why do surface winds generally flow across the isobars at an angle? (AC00-6)

A
  1. Surface friction
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13
Q

At what rate does atmospheric pressure decrease with an increase in altitude? (AC00-6)

A
  1. 1” Hg per 1,000 feet
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