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S5 Geography Weather and Climate, Paper 3: monsoon and extreme weather
S5 Geography Weather and Climate, Paper 3: monsoon and extreme weather
Paper 3 links lapse rate, relative humidity and dew point height, then covers water supply, tropical cyclones and daily range, ending with the relation between temperature and vapour capacity.
Focus Lapse rate times height gives the fall, relative humidity is vapour over capacity, the dew point gap times 100 gives cloud height, and daily range is the same day maximum minus minimum.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Geography: Weather and Climate |
| Level | S5 |
02 Questions (10 items)
- FoundationThe air at the foot of a hill is 30 degrees Celsius and cools 0.6 degree per 100 m. What is the temperature at 1000 m?
- FoundationAir holds 18 grams of vapour per cubic metre and saturation at that temperature is 30 grams. What is the relative humidity?
- FoundationHong Kong receives about 2400 mm of rain a year, so why does it still import Dongjiang water?
- FoundationWhy do tropical cyclones bring both heavy rain and storm surges?
- IntermediateThe air is 32 degrees with a dew point of 20 degrees and cools 1 degree per 100 m. At what height does cloud form?
- IntermediateA station records 29.6 degrees in its hottest month and 16.4 in its coldest. What is the annual range?
- IntermediateAnnual rainfall is 2400 mm and 70 per cent falls from June to September. How much falls in the wet season?
- ChallengeA summit reads 6 degrees and the foot 21 degrees, with a lapse rate of 0.6 degree per 100 m. How high is the hill?
- ChallengeA day peaks at 31 degrees at 2 pm and falls to 23 degrees at 6 am. What is the daily temperature range?
- Error redoError: a student says warmer air can hold less vapour. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 24 degrees Celsius | A thousand metres is ten steps of 100 m, so six degrees are lost and 30 minus 6 is 24. |
| 2 | 60 per cent | Eighteen over thirty times 100 is 60, so the air holds three fifths of its capacity. |
| 3 | Rainfall is concentrated in summer, evaporation is high, catchments are small and demand is large | Rain is heavy but seasonal, and storage is too small to carry the city through the dry months. |
| 4 | Strong rising air condenses large amounts of vapour into rain, and low pressure plus strong winds push sea water onto the coast | Low pressure lifts the sea surface and strong winds push it ashore, flooding low lying coasts. |
| 5 | 1200 m | Twelve degrees must be lost to reach the dew point, which at one degree per 100 m means 1200 m. |
| 6 | 13.2 degrees Celsius | Annual range is hottest minus coldest month, and 29.6 minus 16.4 is 13.2. |
| 7 | 1680 mm | Twenty four hundred times 0.7 is 1680, leaving only 90 mm a month on average for the other eight months. |
| 8 | 2500 m | A difference of 15 degrees divided by 0.6 gives twenty five steps of 100 m, which is 2500 m. |
| 9 | 8 degrees Celsius | Daily range is the same day maximum minus minimum, so 31 minus 23 is 8, and a large range suggests clear dry weather. |
| 10 | Warmer air holds more, roughly six to seven per cent more for each degree, so relative humidity falls if vapour stays the same | Capacity depends on temperature, so warmer air holds more and relative humidity falls when vapour is unchanged. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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