Atmospheric Pressure Flashcards

1
Q

What is static pressure?

A

Weight of air molecules exerting a force per unit area

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2
Q

What happens to static pressure as altitude increases?

A

Static pressure decreases

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3
Q

What is the equation for pressure?

A

Pressure = force (N)/Area (m^2)

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4
Q

What is the ISA pressure lapse rate?

A

1hPa per 30ft of height

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5
Q

What direction does wind move around high pressure in the northern hemisphere?

A

Clockwise

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6
Q

What direction does wind move around low pressure in the northern hemisphere?

A

Anti-clockwise

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7
Q

What is the purpose of isobars on a surface pressure chart?

A

Join places of equal surface pressure

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8
Q

What is a col?

A

An area of pressure distribution which occurs between 2 areas of high pressure and 2 areas of low pressure

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9
Q

What conditions are found in a col?

A

Always light winds, weather conditions dependant on the dominant pressure systems forming it

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10
Q

What is a ridge?

A

An extension of high pressure

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11
Q

What is a trough?

A

An extension of low pressure

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12
Q

What weather is associated with a ridge?

A

Fair weather typical of high pressure regions

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13
Q

What weather is associated with a trough?

A

Cloudy, showery weather typical of a low pressure system

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14
Q

What are the 4 types of pressure datum used by pilots?

A

QFE, QNH, QFF and standard pressure setting

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15
Q

What is QFE?

A

The pressure at field elevation, or at runway threshold

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16
Q

What is QNH?

A

The pressure at sea level (nil height), from the airfield, assuming ISA conditions

17
Q

What is QFF?

A

The pressure at sea level adjusted for actual temperature conditions

18
Q

What is the standard pressure setting?

A

ISA pressure at sea level 1013.25hPa

19
Q

What happens to QNH and QFF above MSL with changing temperature?

A

Warmer than ISA QNH>QFF

Colder than ISA QFF>QNH

20
Q

What happens to QNH and QFF below MSL with changing temperature?

A

Warmer than ISA QFF>QNH

Colder than ISA QNH>QFF

21
Q

What direction does air flow?

A

From high to low pressure

22
Q

What do isobars close together indicate?

A

Strong pressure gradient

Strong wind

23
Q

What happens to pressure in cold air?

A

Falls rapidly with height

24
Q

What happens to pressure in warm air?

A

Falls slowly with height