Atmospheric Pressure

Question 1

Pressure

Answer 1

This is the force per unit area EXERTED against a surface by the weight of the air above that surface
(if the number of air molecules above the surface increases, they will lose, are at greater force on that service – as a result pressure will increase)

Question 2

Station pressure

Answer 2

This is the actual weight of the column of air, extending upwards from the station to the outer limit of the atmosphere of the observing station

Question 3

Mean, sea level pressure
MSL

Answer 3

MSL pressure is station pressure reduced to sea level using the average temperature of the past 12 hours
(The touchstone pressure gauge for all other stations)

Question 4

What is the difference between pressure, and density?

Answer 4

Pressure is the measure of force acting on a unit area. Density is the measure of how closely any given entity is packed.

Question 5

Isobars

Answer 5

A plotted chart of sea level pressures, the connected areas of equal pressure. The resulting lines are isobars. The standard is for hecto pascals apart.

Question 6

Inches of mercury, atmospheres, kilopascals, millibars – conversion

Answer 6

29.92” Hg =
1.0 atm =
101.325 kPa =
1013.25 mb

Question 7

Pressure gradient

Answer 7

The change in pressure over a given distance. (The closer the isobars are together the greater the pressure gradient.)
Isobars practically together = steep pressure gradient. Steeper, the pressure gradient, the stronger the wind.

Question 8

Pressure systems and their variations

Answer 8

High pressure systems
Low pressure systems
Troughs
Ridges
Cols

Question 9

High pressure Centre’s

Answer 9

Sinking air. Air is rotating clockwise and gently flowing outward from the centre in the northern hemisphere (anticyclone) Blue H weather maps

Question 10

A high pressure system has what type of air flow?

Answer 10

Descending air flowing in a clockwise direction

Question 11

What type of weather is associated with a high pressure system?

Answer 11

Fair weather, fewer clouds, good, visibility, light winds, with a chance of early morning fog

Question 12

Low pressure centres

Answer 12

Rising air rotating counterclockwise with a strong inward flow in the northern hemisphere (cyclone)
Red L weather charts

Question 13

What are low pressure centres caused by?

Answer 13

Convergence of air coming into a region being forced to rise. This causes the air to expand and become less dense as it rises.

Question 14

What type of weather is expected with low pressure systems?

Answer 14

Thunderstorms, rain, hail, snow

Question 15

Troughs

Answer 15

An elongated area of low pressure, likely to bring about wind shift at the surface, low pressure trough symbol is a long, purple line.

Question 16

Weather associated with troughs

Answer 16

Clouds, showers, and wind shift

Question 17

Ridges

Answer 17

These are areas of elongated, high pressure with a low pressure on each side. Fair weather is associated with. The symbol resembles sawtooth pattern on a map.

Question 18

COL

Answer 18

This is a neutral region between two highs and two lows. Weather at a col tends to be unsettled. Expect fog in winter time, expect showers and thunderstorms in summertime.

Question 19

Boyle’s law

Answer 19

Warm air will take up a greater volume than cold air.

Question 20

Altimeter in summer vs winter

Answer 20

At the same, given altimeter, setting an aircraft will be much closer to the obstacle in winter time, as opposed to the summertime.