Reading Weather Patterns — Drills · Grade 9 Science

Chapter: Atmosphere & Weather

What these drills covers

By the end of Reading Weather Patterns you should be able to:

8 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: isobar, station model, meteorologist, prevailing westerlies, relative humidity, dew point.

Problem 1

Isobars on a weather map join points of equal
  1. temperature
  2. pressure
  3. humidity
  4. rainfall
Answer and explanation

pressure

Iso- means equal and -bar refers to pressure.

Problem 2

In the mid-latitudes, weather systems generally move
  1. east to west
  2. west to east
  3. north to south
  4. they do not move
Answer and explanation

west to east

Prevailing westerlies carry systems eastward, which is why forecasters watch upstream conditions.

Problem 3

A front is 300 km away and moving at 25 km/h. In how many hours will it arrive?
Answer and explanation

12 hours

300 / 25 = 12 hours.

Problem 4

Relative humidity of 100 percent means the air
  1. contains no water
  2. is saturated at its current temperature
  3. is at 100 °C
  4. cannot hold any water
Answer and explanation

is saturated at its current temperature

It holds as much vapour as it can at that temperature, so further cooling causes condensation.

Problem 5

A station reports 18 °C with a dew point of 18 °C. What is the relative humidity, as a percentage?
Answer and explanation

100 %

When temperature equals dew point the air is saturated, so relative humidity is 100 percent.

Problem 6

Dew point is the temperature at which air
  1. freezes
  2. becomes saturated and condensation begins
  3. boils
  4. stops moving
Answer and explanation

becomes saturated and condensation begins

A dew point close to the air temperature indicates humid air and likely fog or cloud.

Problem 7

Explain how a station model packs several measurements into one symbol on a map.
Answer and explanation

A station model places each quantity in a fixed position around a circle: temperature and dew point on the left, pressure on the upper right, cloud cover shown by how much of the circle is filled, and a wind barb whose shaft shows direction and whose feathers show speed. Because every station uses the same convention, a forecaster can read a whole map at a glance and compare places directly.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

Explain why a forecast should be stated with a probability rather than a single outcome.
Answer and explanation

The atmosphere's behaviour cannot be measured completely or modelled exactly, so several outcomes remain consistent with what is known. A probability reports how much of that uncertainty supports each outcome, which is more useful and more honest than a single prediction that will sometimes be wrong without warning. It also lets people make decisions proportionate to the risk.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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