Quick Summary
- Weather stations measure elements like temperature, rainfall, wind, humidity, and pressure
- The Stevenson screen protects thermometers from direct sunlight and rain
- Nigeria’s weather stations are managed by the Nigerian Meteorological Agency (NiMet)
- Common instruments include rain gauge, barometer, anemometer, and wind vane
- Accurate weather data helps farmers, pilots, and disaster management agencies
What is a Weather Station?
A weather station is like a special outdoor laboratory where scientists measure the atmosphere. Think of it as the place where your weather app gets its information. In Nigeria, the Nigerian Meteorological Agency (NiMet) operates weather stations in cities like Lagos, Abuja, Kano, and Port Harcourt.
These stations work 24 hours a day, collecting data about rain, sun, wind, and temperature. The information helps predict if tomorrow will be rainy or sunny. This is important for farmers planning when to plant crops, pilots planning flights, and NEMA (National Emergency Management Agency) preparing for floods or droughts.
Main Components of a Weather Station
1. The Stevenson Screen
This is a white wooden box raised about 1.2 meters above the ground. The box has slats (thin strips of wood) on all sides to let air flow through while blocking direct sunlight and rain. Inside the Stevenson screen, you find four types of thermometers:
- Maximum thermometer: Records the highest temperature of the day
- Minimum thermometer: Records the lowest temperature of the day
- Dry bulb thermometer: Measures current air temperature
- Wet bulb thermometer: Measures humidity (moisture in the air)
The screen is painted white to reflect heat. It faces away from the sun and sits on short legs so air can move underneath. In Lagos, during harmattan season, you might see readings showing very low humidity on the wet bulb thermometer.
2. Rain Gauge
This instrument measures how much rain falls in millimeters. It looks like a metal cylinder with a funnel on top. When rain falls into the funnel, it collects in a measuring tube inside. After rain, the observer reads the measurement and empties the gauge.
Nigerian farmers in states like Oyo and Kaduna use rainfall data to know the best planting seasons. Too little rain means drought; too much can cause floods like those seen in Kogi State.
3. Barometer
A barometer measures atmospheric pressure (the weight of air pressing down on Earth). When pressure drops suddenly, it often means rain is coming. When pressure rises, expect clear weather.
There are two types:
- Mercury barometer: Uses a tube of mercury
- Aneroid barometer: Uses a metal chamber (more common in modern stations)
4. Anemometer
This instrument measures wind speed. It has three or four cups attached to arms that spin when wind blows. The faster the wind, the faster the cups spin. Wind speed is measured in kilometers per hour or knots.
During the rainy season in Nigeria, strong winds can reach 60-80 km/h, especially during thunderstorms.
5. Wind Vane
A wind vane shows wind direction. It has an arrow that points where the wind is coming from. If the arrow points north, the wind is a “north wind” (blowing from the north).
In Nigeria, the harmattan wind comes from the northeast, bringing dust from the Sahara Desert. Weather stations record this as a northeast wind.
6. Sunshine Recorder
This device measures how many hours of sunshine occur each day. It uses a glass ball that focuses sunlight onto a card. The sun’s heat burns a line on the card as it moves across the sky.
7. Hygrometer
A hygrometer measures relative humidity (how much moisture is in the air). High humidity makes the air feel sticky and uncomfortable, like in Port Harcourt during the wet season. Low humidity makes the air dry, like during harmattan.
Comparison of Weather Instruments
| Instrument | Measures | Unit | Location |
|---|---|---|---|
| Maximum thermometer | Highest temperature | Degrees Celsius (°C) | Inside Stevenson screen |
| Minimum thermometer | Lowest temperature | Degrees Celsius (°C) | Inside Stevenson screen |
| Rain gauge | Rainfall amount | Millimeters (mm) | Open ground, away from trees |
| Barometer | Atmospheric pressure | Millibars (mb) | Indoors |
| Anemometer | Wind speed | Kilometers per hour (km/h) | High pole in open area |
| Wind vane | Wind direction | Compass points (N, S, E, W) | High pole in open area |
| Hygrometer | Relative humidity | Percentage (%) | Inside Stevenson screen |
How a Weather Station Site is Set Up
Weather stations must be in open areas away from tall buildings and trees. This ensures instruments measure actual weather conditions, not effects from nearby objects. The ideal site has:
- Level ground covered with short grass
- No buildings within 30 meters
- Clear view of the sky in all directions
- A fence to keep people and animals out
- Good drainage so water doesn’t pool after rain
In Nigerian cities, finding such sites is difficult because of buildings and development. NiMet weather stations in Lagos often use rooftops or cleared areas in airports.
Reading and Recording Weather Data
Weather observers visit the station at fixed times each day (usually morning and evening). They:
- Read each instrument carefully
- Record the numbers in a logbook
- Reset instruments that need it (like the maximum and minimum thermometers)
- Send data to NiMet headquarters
- Check that all instruments are working properly
Today, many weather stations use automatic sensors that send data by computer or phone. This reduces human error and provides real-time information.
Importance of Weather Stations in Nigeria
For Agriculture
Farmers need to know when rains will start and end. In states like Benue (the “Food Basket of the Nation”), farmers use weather forecasts to plan planting dates for yam, cassava, and rice. Wrong timing can lead to crop failure and hunger.
For Aviation
Pilots at Murtala Muhammed Airport in Lagos and Nnamdi Azikiwe Airport in Abuja rely on weather reports before takeoff. Strong winds, thunderstorms, or poor visibility can make flying dangerous.
For Disaster Management
NEMA uses weather data to predict floods and warn communities. Heavy rainfall warnings help people in areas like Lokoja (where Rivers Niger and Benue meet) prepare for flooding.
For Health
Hot, humid weather increases malaria transmission because mosquitoes breed faster. Health officials use climate data to predict malaria outbreaks and distribute nets and drugs.
For Education and Research
Universities and research centers study long-term weather patterns (climate) to understand changes over time. This helps Nigeria prepare for climate change effects like desertification in the north.
Common Exam Mistakes
WAEC Chief Examiner Reports show students often:
- Confuse thermometers: They mix up maximum and minimum thermometers or say the Stevenson screen contains only one thermometer (it has four)
- Forget the Stevenson screen color: Many don’t explain why it’s painted white (to reflect sunlight and keep thermometers cool)
- Name instruments without functions: Listing “barometer” without saying it measures atmospheric pressure
- Wrong units: Saying rainfall is in liters instead of millimeters, or wind speed in meters instead of kilometers per hour
- Poor site descriptions: Not mentioning that weather stations need open, level ground away from buildings
- Confusing weather and climate: Weather is day-to-day conditions; climate is average weather over 30+ years
Practice Questions
Multiple Choice Questions
1. Which instrument measures atmospheric pressure?
a) Anemometer
b) Barometer ✓
c) Hygrometer
d) Wind vane
2. Why is the Stevenson screen painted white?
a) To make it visible from far away
b) To reflect heat and keep instruments cool ✓
c) To attract rain
d) To prevent rust
3. The wind vane measures:
a) Wind speed
b) Wind temperature
c) Wind direction ✓
d) Wind pressure
4. How many thermometers are typically found in a Stevenson screen?
a) One
b) Two
c) Three
d) Four ✓
Essay/Theory Questions
1. Describe the Stevenson screen and explain why it is important in a weather station. (5 marks)
Examiner’s tip: Define what it is (1 mark), describe its features – white color, raised height, slatted sides (2 marks), and explain its function – protects thermometers from direct sun and rain while allowing air circulation (2 marks).
2. State five instruments found in a weather station and explain what each measures. (10 marks)
Examiner’s tip: Name the instrument (1 mark) and its function (1 mark) for each. Examples: rain gauge (rainfall in mm), barometer (atmospheric pressure), anemometer (wind speed), wind vane (wind direction), maximum thermometer (highest temperature).
3. Explain four reasons why weather stations are important in Nigeria. (8 marks)
Examiner’s tip: Give each reason (1 mark) and explain it with a Nigerian example (1 mark). Don’t just list; show understanding by explaining how weather data helps agriculture, aviation, disaster management, or health.
Memory Aids
Remember the 4 thermometers in Stevenson screen:
M-M-D-W = Maximum, Minimum, Dry bulb, Wet bulb
Remember what wind vane vs anemometer does:
Wind VANE shows which way (direction)
ANEMOmeter shows speed (think “anime” = fast action!)
Stevenson Screen features:
W-R-S-L = White paint, Raised on legs, Slatted sides, Louvered (allows air flow)
Related Topics
- Elements of Weather and Climate
- Climatic Types in Nigeria
- Rainfall Distribution in West Africa
- Temperature and Its Measurement
- Wind Systems in Nigeria