Lesson 10

Question 1

What are synoptic features?

Answer 1

Synoptic features are weather patterns that cover a large area

Question 2

Wind refers to a horizontal movement of air from an area of low pressure to an area of high pressure (true or false)

Answer 2

FALSE - It moves from high pressure to low pressure`

Question 3

What does a knot represent as a unit of measure?

Answer 3

One knot is equal to one nautical mile per hour

Question 4

Isobars are curved lines that connect points of equal pressure and show variations in pressure
at any given time. What is the unit of measurement for an isobar?

Answer 4

Isobars are measured in hectopascals (hPa)

Question 5

There are 2 basic cloud forms - what are they?

Answer 5

Stratiform or stratus-type clouds which appear in horizontal layers.
Cumuliform or cumulus-type clouds have a more prominent vertical formation and usually do
not cover a large area.

Question 6

What are the four basic types of cumuliform clouds?

Answer 6

Cumulus (CU)
Towering cumulus (TCU)
Cumulonimbus (CB)
Altocumulus castellanus (ACC)

Question 7

Name the four types of pressure systems

Answer 7

Pressure systems include high-pressure areas, low-pressure areas, troughs, and ridges.

Question 8

In what direction will the air flow around a high-pressure system?

Answer 8

Clockwise

Question 9

What are other names for a high-pressure area?

Answer 9

A high-pressure area may also be called a high or an anticyclone.

Question 10

In what direction will the air flow around a low pressure system?

Answer 10

Air circulates counter-clockwise around the centre of low-pressure systems

Question 11

What are other names for a low-pressure area?

Answer 11

A low-pressure area may also be called a low, a cyclone, or a depression.

Question 12

A trough is associated with a low-pressure system whereas a ridge is associated with a high-pressure system. (True or False)

Answer 12

True

A trough is essentially an elongated region of relatively low atmospheric pressure, often
associated with fronts.

A ridge is essentially an elongated region of relatively high atmospheric pressure.

Question 13

Define pressure gradient

Answer 13

Pressure gradient is the rate of change of pressure with horizontal distance measured in
kilometres.

Question 14

Define the Coriolis force

Answer 14

The Coriolis force is caused by the Earth’s rotation.

In the northern hemisphere, as the air moves from a high-pressure area to a low-pressure area, the Coriolis force deflects the moving air to the right. This is because the rotating Earth has a counter-clockwise spin in the northern
hemisphere.

The Coriolis force does not cause wind; it affects the direction of the air movement. Affected air
flows parallel to the isobars. If the Earth didn’t rotate, the wind would flow directly from a high- to
a low-pressure area.

Question 15

What is Buys Ballot’s law?

Answer 15

According to Buys Ballot’s Law, the wind is at the person’s back, so the
lower pressure is to the left

In the northern hemisphere, the pressure gradient force and the Coriolis force combine to cause
the air to flow parallel to the isobars, clockwise around a high, and counter-clockwise around a
low.

Plainly stated, with the wind at your back in the northern hemisphere, the area of lower pressure
lies to your left.

Question 16

Veering winds change in which direction

Answer 16

Clockwise - Example: wind is veering from south (180°) to west (270°). The wind direction has changed in a clockwise direction.

Question 17

Backing winds change in which direction

Answer 17

Counter-clockwise - Example:wind is backing from south (180°) to east (090°). The wind direction has
changed in a counter-clockwise direction.

Question 18

A lifting agent is a force that pushes air upwards. For clouds and precipitation to occur, air must
be lifted so that it can cool and condense. What are the 5 lifting agents?

Answer 18

• Convection
• Orographic lift
• Frontal lift
• Mechanical turbulence
• Convergence

Question 19

Define what an air mass is

Answer 19

An air mass is a large section of the troposphere with relatively uniform properties of
temperature and moisture in the horizontal.

Question 20

What are the 2 types of air masses

Answer 20

• Maritime air masses form over large bodies of water and are humid.
• Continental air masses form over large land areas and are dry.

Question 21

What are the 3 terms that describe the temperature of air masses

Answer 21

• Arctic air masses are cold and form in the Arctic or at high latitudes.
• Polar air masses are temperate. Despite their name, polar air masses actually form in
  the temperate zones (permafrost line to 30°N) by the heating of an Arctic air mass or the
  cooling of a tropical air mass.
• Tropical air masses are warm and form in the tropics or low latitudes (between 30°N and
  the equator).

Question 22

What are the four air masses commonly found in North America?

Answer 22

Continental Arctic (cA) (in winter only)
* Maritime Arctic (mA)
* Maritime Polar (mP)
* Maritime Tropical (mT)

Question 23

What is a front?

Answer 23

A front is the transition zone between two air masses.