CARA'S TIPSWeather & climate: elements, measurement, types & climate change
JAMBWAECNECO
What the syllabus asks
JAMB: Physical Geography F: weather and climate: elements, instruments and Stevenson screen, factors controlling climate, climate charts, classification (Greek and Köppen), major climate types, climate change: causes, effects and remedies
WAEC: Weather and climate: elements of weather and climate, their measurement and recording; factors affecting climate; major climatic types; climate change (Nigeria)
NECO: Weather and climate: elements of weather and climate, their measurement and recording; factors affecting climate; major climatic types; climate change (Nigeria)
What you will learn
- Distinguish between weather and climate and list the elements.
- Name the instruments for each element, explain how they work and describe the Stevenson screen.
- Calculate mean, range, totals and relative humidity from data.
- Explain pressure belts and planetary winds, land and sea breezes and air masses.
- Explain humidity, condensation, cloud types and the three types of rainfall.
- Explain the factors that control climate.
- Classify climates using the Greek and Köppen systems and describe the major climate types.
- Interpret climate graphs and identify climate types.
- Explain the causes, effects and remedies of climate change, with Nigerian examples.
Key points
- Weather is short-term; climate is the 30-year-plus average.
- Elements: temperature, rainfall, humidity, pressure, wind, sunshine, cloud; each has an instrument.
- The Stevenson screen is white, louvred, double-roofed, on legs about 1.2 m high, on grass, door away from the sun.
- Mean = (max + min) ÷ 2; range = max − min; annual range uses monthly means.
- Temperature falls about 6.5 °C per 1,000 m.
- Air flows from high to low pressure; Coriolis deflects it right in the north, left in the south.
- Pressure belts: equatorial low, sub-tropical highs, sub-polar lows, polar highs; winds: trades, westerlies, polar easterlies.
- RH falls as the wet-bulb depression grows; air saturates at the dew point.
- Rainfall types: convectional, relief and frontal.
- Factors: latitude, altitude, distance from sea, ocean currents, winds/air masses, relief, pressure belts, vegetation.
- Köppen groups A, B, C, D, E (and H) use temperature and rainfall values.
- Climate change is driven by greenhouse gases; respond with mitigation and adaptation.
Start here: Weather, climate and the atmosphere
When your mother says “Bring an umbrella, it looks like rain,” she is talking about weather. When a farmer in Kebbi says “We plant millet in June because the rains come late here,” he is talking about climate.
| Weather | Climate |
|---|---|
| Short period (hours, days) | Long period (30+ years) |
| Changes quickly | Fairly stable |
| Small area | Large area/region |
| Studied by meteorology | Studied by climatology |
The elements
Temperature, precipitation, humidity, atmospheric pressure, wind (speed and direction), sunshine, and cloud cover. Visibility is also recorded at airports.
Layers of the atmosphere
The troposphere is thickest at the equator (about 16–18 km) and thinnest at the poles (about 8 km). Almost all water vapour and clouds are in it. The ozone layer in the stratosphere absorbs harmful ultraviolet rays.
Composition of dry air (by volume, rounded)
| Gas | % |
|---|---|
| Nitrogen | 78 |
| Oxygen | 21 |
| Argon | 0.9 |
| Carbon dioxide | about 0.04 |
Water vapour varies from almost 0 to about 4%.
Classify each statement as weather or climate: (a) “Jos was foggy this morning.” (b) “Sokoto has a long dry season.”
- (a) A particular time → weather.
- (b) A long-term average → climate.
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Practice questions
- weather
- climate
- relief
- vegetation
Show answer
A: weather
Climate is the average over about 30 years.
- barometer
- hygrometer
- wind vane
- rain gauge
Show answer
D: rain gauge
Readings are taken daily.
- anemometer
- rain gauge
- barometer
- thermometer
Show answer
C: barometer
Units: millibars or hectopascals.
- sunshine recorder
- hygrometer (wet-and-dry bulb thermometer)
- barometer
- anemometer
Show answer
B: hygrometer (wet-and-dry bulb thermometer)
The difference between the bulbs shows dryness of the air.
- reflect the sun’s rays
- absorb heat
- make it visible
- stop rain
Show answer
A: reflect the sun’s rays
It shades the thermometers so they record air temperature.
Key words
- Weather
- The condition of the atmosphere at a place at a particular time.
- Climate
- The average weather conditions of a place over a long period, usually 30 years or more.
- Insolation
- Incoming solar radiation reaching the earth’s surface.
- Lapse rate
- The rate at which temperature falls with height; about 6.5 °C per 1,000 m on average.
- Isotherm
- A line on a map joining places of equal temperature.
- Isobar
- A line joining places of equal atmospheric pressure.
- Isohyet
- A line joining places of equal rainfall.
- Relative humidity
- The amount of water vapour in the air compared with the maximum it could hold at that temperature, as a percentage.
- Dew point
- The temperature at which air becomes saturated and condensation begins.
- Condensation
- The change of water vapour into liquid water droplets.
- Precipitation
- Water falling from the atmosphere: rain, snow, sleet, hail, drizzle.
- Convectional rainfall
- Rain formed when strongly heated air rises, cools and condenses.
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