Geography · Lesson 21

Practical geography 6: weather station, instruments, fieldwork reports and Paper 3 timing

WAECNECO

What the syllabus asks

WAEC: weather and climate (elements, measurement and recording: weather instruments, the Stevenson screen, school weather station); fieldwork and field reports; Paper 3 examination technique

NECO: weather and climate (elements, measurement and recording: weather instruments, the Stevenson screen, school weather station); fieldwork and field reports; Paper 3 examination technique

What you will learn

Describe the Stevenson screen and site a school weather station.
Read Six’s thermometer and calculate daily mean and range.
Find relative humidity from wet- and dry-bulb readings.
Measure rainfall and convert volume to depth.
Describe instruments for pressure, wind and sunshine.
Draw and interpret a wind rose.
Plan and report a field study.
Plan time and question choice for Paper 3.

Key points

The Stevenson screen gives shade with free air flow.
Read Six’s indices at their lower ends; reset with a magnet.
Daily mean = (max + min) ÷ 2.
Bigger wet-bulb depression = drier air.
Rainfall = volume ÷ funnel area.
Wind is named from where it blows.
Wind rose bars ∝ frequency; calms in the centre.
Instrument answers: diagram, principle, reading, siting, precaution.
Field report: aim → methods → results → conclusion → problems.
Paper 3: 35 + 25 + 25 + 25 = 110 minutes.

Start here: Concept summary: the weather station and fieldwork

Two topics complete the practical-geography syllabus: the measurement of weather (instruments, readings and calculations) and fieldwork (planning, carrying out and reporting a field study). The WAEC syllabus places weather and climate, “their measurement and recording”, in Paper 3’s physical geography, and expects candidates to be able to describe a school weather station and to work with readings; fieldwork appears as questions on how a study was conducted and reported. JAMB includes “weather instruments” and field studies in its objective items.

This unit covers each instrument (what it measures, how it works, how it is read and where it is placed), the calculations you must do from readings (mean, range, relative humidity, rainfall depth, wind-rose percentages), how to present weather data, how to write a field-trip report, and finally the whole-paper exam technique for Paper 3. The readings in the worked examples are illustrative values for an imaginary school weather station at Oke-Ofa; every calculation has been checked by computer.

Instrument descriptions are deliberately practical: examiners reward answers that show you have actually seen and used the instruments. If your school has a weather station, take one week of readings yourself using the booking sheet in section 6.7, and you will never forget how each instrument works.

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Practice questions

1. The Stevenson screen protects thermometers from

direct sunlight and rain
wind measurement
humidity
air circulation

Show answer

A: direct sunlight and rain
Louvred white box.

2. Six’s thermometer records

humidity
pressure
sunshine
maximum and minimum temperatures

Show answer

D: maximum and minimum temperatures
U-tube with indices.

3. The wet- and dry-bulb thermometers (hygrometer) measure

wind speed
pressure
relative humidity
rainfall

Show answer

C: relative humidity
Using the depression.

4. A large wet-bulb depression indicates

fog
dry air
humid air
rain

Show answer

B: dry air
More evaporation.

5. A rain gauge is read

daily at a fixed time
only when it rains heavily
weekly
monthly

Show answer

A: daily at a fixed time
Usually 9 a.m.

Key words

Stevenson screen: Louvred white box housing thermometers in shade.
Six’s thermometer: Records maximum and minimum temperatures.
Hygrometer: Wet- and dry-bulb thermometers for humidity.
Relative humidity: Water vapour present as a percentage of the maximum possible.
Wet-bulb depression: Dry-bulb minus wet-bulb temperature.
Rain gauge: Instrument for measuring rainfall in mm.
Barometer: Instrument for measuring air pressure.
Anemometer: Instrument for measuring wind speed.
Wind vane: Shows the direction the wind blows from.
Campbell-Stokes recorder: Records hours of bright sunshine.
Okta: One eighth of the sky, unit of cloud cover.
Wind rose: Diagram of the frequency of winds from each direction.

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