Lesson 112 - Surface Pressure And Pressure Levels

Front 1

State the uses of atmospheric pressure in meteorology

Back 1

- analyze typical atmospheric features
- estimate air motion
- identify significant weather patterns
- relate pressure to weather conditions
- set aircraft altimeters for aviation

112.1.1

Front 2

Describe the relationship between pressure, area, and force

Back 2

p=F/A, where p=pressure, F=force, A=area

- force has direct relationship with pressure. As F grows, so proportionally will p
- area has inverse relationship with pressure. As A grows, p will decrease proportionally

112.1.2

Front 3

State the two factors which control the surface pressure

Back 3

- change in temperature
- change in moisture content

Both change density of column of air, therefore affecting mass.

Heating=expansion=decreased surface pressure
Cooling=contraction=increased surface pressure

112.1.3

Front 4

Define an isobar

Back 4

A line along which pressure is constant

112.1.4

Front 5

Describe the diurnal change to surface pressure

Back 5

- variations due to rhythmic expansion/contraction of atmosphere due to alternating daytime heating/nighttime cooling
- 2 pressure minima at 0400 and 1600
- 2 pressure maxima at 1000 and 2200

112.1.6

Front 6

State the use of pressure levels in meteorology

Back 6

- displays the state of atmosphere at specific levles of pressure altitude
- upper air charts depict height variations above MSL and height patterns
- analysis provides info pursuant to safety and efficiency of flight ops

112.2.1

Front 7

Define the hydrostatic equilibrium

Back 7

- exists in atmosphere when vertical component of Pressure Gradient Force at any given level is in exact balance with force of gravity at that level

112.2.2

Front 8

Describe the relationship between the thickness of an atmospheric layer, the density of the air, and the average temperature

Back 8

Thickness increases if temp increases:
- warm air less dense, expands, and thicker layer
- cold air more dense, compresses, and thinner layer

112.2.3

Front 9

State the two factors which affect the height of a pressure level

Back 9

- value of MSL
- mean temp of column of air beneath the pressure level

112.2.4

Front 10

Given a variation in one of the two factors which affect the height of a pressure level, state its effect

Back 10

- height of pressure level higher when MSL pressure higher and/or column temps higher
- height of pressure level lower when MSL pressure lower and/or column temps lower

112.2.5

Front 11

Given a diagram depicting the vertical variations of pressure levels identify a cold high, cold low, warm low, and warm high

Back 11

Cold high:
- high surface pressure and upper level lower pressure
Cold low:
- low surface pressure and upper level lower pressure
Warm low:
- low surface pressure and upper level high pressure
Warm high:
- high surface pressure and upper level high pressure

112.2.6

Front 12

Explain the seasonal variations in the height of a pressure level in mid latitude

Back 12

In winter, average pressure height in troposphere becomes lower because mean temp in the troposphere becomes colder

112.2.7

Front 13

Explain the variation in the height of a pressure level from Pole to the Equator

Back 13

Since temps get warmer approaching the equator, and pressure level height directly linked to temps, height of pressure levels rise as you proceed from Pole to the equator

112.2.8