Year 10 Science · Unit 4 · Lesson 1
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Learning Goals
Compare two
Complete the table to compare El Niño and La Niña. Fill in all blank cells.
| Feature | El Niño | La Niña |
|---|---|---|
| Pacific Ocean surface water temperature (central/eastern Pacific) | ||
| Effect on eastern Australia's rainfall | ||
| Risk for Queensland and NSW | ||
| Agricultural impact (farming) |
Real-world context
A farmer in the Darling Downs (QLD), one of Australia's most productive grain-growing regions, wants to decide whether to plant a wheat crop in April. The Bureau of Meteorology (BOM) has issued a seasonal outlook predicting La Niña conditions for the coming winter. Wheat requires moderate rainfall during its growing season (April–September) but is damaged by flooding.
(a) What climate pattern should the farmer expect during La Niña conditions? Use specific details about rainfall and the western Pacific.
(b) What specific weather data would the farmer want to monitor during April–September (not just the seasonal forecast)? Name at least two types of weather data.
(c) Explain the difference between the BOM's La Niña climate prediction and a daily weather forecast. Why is this difference important for the farmer's planning?
Wrap Up
In one sentence, what was the main idea of this lesson?
Warm Up, Compare two
Pacific Ocean surface water temperature (central/eastern Pacific): El Niño: warmer than usual, because the warm pool shifts eastward. La Niña: cooler than usual, because the warm water stays piled up in the west.
Effect on eastern Australia’s rainfall: El Niño: reduced, below average. La Niña: increased, above average.
Risk for Queensland and NSW: El Niño: drought, water restrictions and a heightened bushfire season. La Niña: flooding, waterlogged ground and storm damage.
Agricultural impact: El Niño: poor germination and reduced yields, stock feed and water shortages, crops may fail outright. La Niña: good growing rainfall, but a real risk of flood damage, waterlogged roots, disease, and harvest delayed or lost to wet paddocks.
The agricultural row is the one that rewards thought. La Niña is not simply “good for farmers” — more rain helps a crop grow and can also destroy it at harvest, which is exactly the tension the Your Turn scenario turns on.
Your Turn, Real-world context
(a) During La Niña the warm ocean water stays in the western Pacific, close to Australia. Warm water evaporates readily, so more moisture is carried over the continent and eastern Australia receives above-average rainfall. For the Darling Downs that means a wetter than normal April–September, with a raised risk of heavy falls and flooding rather than the moderate rain wheat wants. [2 marks: 1 for above-average rainfall, 1 for the mechanism naming warm water remaining in the western Pacific and driving extra moisture over Australia.]
(b) Any two of: daily and weekly rainfall totals; soil moisture; daily maximum and minimum temperature, especially frost risk during winter; short-range forecasts and severe weather or flood warnings; humidity; wind. The point is that these are day-to-day measurements, not a seasonal outlook — the farmer needs them to decide when to sow, spray and harvest, which the outlook cannot tell them. [2 marks: 1 for each valid type of weather data. Credit a student who explains why daily data is needed alongside the outlook.]
(c) The BOM’s La Niña outlook is a climate prediction: a statement of probability about average conditions across a whole season, months ahead, built from slow-moving ocean and atmosphere patterns. A daily forecast is a weather prediction: specific conditions at a specific place over the next few days, and beyond about a week it loses skill. The difference matters because the two decisions have different timescales. The seasonal outlook is what the farmer uses in April to decide whether to plant wheat at all and which variety; the daily forecast is what they use through the season to decide when to sow, spray or bring the harvest in. Using one for the other’s job is the error — the outlook cannot name the day it will rain, and the forecast cannot see to September. [3 marks: 1 for the outlook being seasonal and probabilistic, 1 for the forecast being short-range and specific, 1 for linking each to the decision it actually supports.]