What this lesson teaches
I can tell weather from climate, name the main climate types, and describe the hazards each brings.
Syllabus K229, Topic 2.1, Key Question 1. What is weather and climate?
Make a guess
Mumbai and Singapore each get about 2,100 to 2,200 mm of rain a year. Do they have the same kind of rainfall?
- No. Mumbai gets most of it in four months.
- Yes, because the yearly totals are almost equal.
- No. Mumbai is much drier in most months.
- Yes, because both are in Asia.
Show the answer
No. Mumbai gets most of it in four months.
Totals can match while the spread differs. About 95% of Mumbai's rain falls from June to September, while every month in Singapore gets over 100 mm.
Name a climate type from three readings: the temperature range, the yearly rainfall total, and how that rain is spread across the year.
A climate type is a pattern of temperature and rainfall that many places share. To name one from a climate graph, take three readings. First, the temperature range: the highest monthly mean minus the lowest. Second, the total rainfall in a year: add the twelve monthly bars. Third, the spread: which months are wettest and driest, and is there a dry season?
Changi in Singapore has a tropical equatorial climate. Monthly means stay between 26.8 and 28.6 degrees C, a range of only 1.8 degrees C. About 2,113 mm of rain falls in a year, and every month gets more than 100 mm. Singapore is near the equator, so the midday sun is high all year. Strong heating makes warm, moist air rise almost every day, which forms convectional rain.
Mumbai in India, about 19 degrees north, has a tropical monsoon climate. At the Colaba station the yearly total is about 2,213 mm, close to Singapore's. But about 95% of it falls from June to September, when the southwest monsoon brings moist air from the Arabian Sea. January to April each get less than 1 mm. The range is 5.9 degrees C. May is the hottest month, at 30.7 degrees C, because the sun is high and the rains have not yet brought cloud.
London in the United Kingdom, about 51 degrees north, has a cool temperate climate. At Heathrow, monthly means run from 5.6 degrees C in January to 19.0 degrees C in July, a range of 13.4 degrees C. Far from the equator, the winter sun is low and days are short, so winters are cool. Rainfall is only about 616 mm a year, but it falls in every month. It ranges from 38.8 mm in March to 66.6 mm in November.
Sort these
Which climate type does each clue point to?
Groups: Tropical equatorial, Tropical monsoon, Cool temperate.
- Four very wet months, then several months with almost no rain
- Range over 10 degrees C, with cool winters and mild summers
- The hottest month comes just before the rains arrive
- Temperature range under 2 degrees C, with every month above 100 mm of rain
- Heavy afternoon showers from rising warm air almost every day
- Only about 600 mm a year, but some rain falls in every month
Show the answer
Tropical equatorial
- Temperature range under 2 degrees C, with every month above 100 mm of rain A tiny range and rain all year are signs of a place near the equator with a high sun every month.
- Heavy afternoon showers from rising warm air almost every day Strong daily heating near the equator drives convectional rain, typical of an equatorial climate.
Tropical monsoon
- Four very wet months, then several months with almost no rain A clear wet and dry season comes from seasonal winds, which marks a monsoon climate.
- The hottest month comes just before the rains arrive The sun is high and there is no cloud yet, so temperatures peak before the wet season.
Cool temperate
- Range over 10 degrees C, with cool winters and mild summers A large range comes from a low winter sun and short days far from the equator.
- Only about 600 mm a year, but some rain falls in every month Modest rain spread across all seasons fits a cool temperate climate, not a tropical one.
In an exam answer, describe before you explain. Give the pattern, quote figures with units and months, and do the calculation. Then compare places directly, using words such as "higher", "more evenly spread" or "concentrated". Last, explain the difference with latitude, winds or distance from the sea. Always check the rainfall axis first, because two graphs can use very different scales.
- Tropical equatorial
- Small temperature range, rain in every month (Changi: range 1.8 degrees C, about 2,113 mm).
- Tropical monsoon
- Warm all year, one very wet season and a long dry season (Mumbai: about 95% of rain in June to September).
- Cool temperate
- Large temperature range, rain spread through the year (London: range 13.4 degrees C, about 616 mm).
Step by step
Range
Highest monthly mean temperature minus the lowest.
Total
Add the twelve monthly rainfall figures.
Spread
Name the wettest and driest months, and any dry season.
Compare and explain
Use comparison words, then latitude, winds or the sea.
Worked example: A full comparison in four sentences
Changi and Mumbai get similar yearly rainfall, about 2,113 mm and 2,213 mm. Changi's rain falls in every month, but about 95% of Mumbai's falls from June to September, and January to April each get under 1 mm. Mumbai's temperature range of 5.9 degrees C is larger than Changi's 1.8 degrees C. This is because Mumbai, at 19 degrees N, is farther from the equator, and its rain depends on the seasonal southwest monsoon.
Try it step by step
Problem 1
Changi, Singapore. Monthly means (degrees C), January to December: 26.8, 27.3, 27.8, 28.2, 28.6, 28.5, 28.2, 28.1, 28.0, 27.9, 27.2, 26.8.
Show the working
- Find the highest monthly mean: The highest is 28.6 degrees C, in May.
- Find the lowest monthly mean: The lowest is 26.8 degrees C, in January and December.
- Subtract to get the range: 28.6 - 26.8 = 1.8 degrees C.
Problem 2
Mumbai (Colaba), India. Monthly means (degrees C), January to December: 24.8, 25.4, 27.4, 29.1, 30.7, 29.4, 27.7, 27.6, 27.9, 29.1, 28.7, 26.7.
Show the working
- Find the highest monthly mean: The highest is 30.7 degrees C, in May, just before the monsoon rains.
- Find the lowest monthly mean: The lowest is 24.8 degrees C, in January.
- Subtract to get the range: 30.7 - 24.8 = 5.9 degrees C.
Problem 3
London (Heathrow), UK. Monthly means (degrees C), January to December: 5.6, 5.8, 7.9, 10.5, 13.7, 16.8, 19.0, 18.7, 15.9, 12.3, 8.4, 5.9.
Show the working
- Find the highest monthly mean: The highest is 19.0 degrees C, in July.
- Find the lowest monthly mean: The lowest is 5.6 degrees C, in January.
- Subtract to get the range: 19.0 - 5.6 = 13.4 degrees C.
Watch out for this
Mumbai gets more rain than Singapore, so it must be wetter all year.
The yearly totals are similar, but Mumbai's rain comes in four months. For most of the year Mumbai is much drier than Singapore. Always look at the spread, not just the total.
Check your understanding
A station's monthly means run from 4 to 18 degrees C, and every month gets 40 to 70 mm of rain. Which climate type fits best?
- Tropical equatorial, because no month there goes without rain.
- Tropical monsoon, because rain falls in every month.
- Cool temperate, because of the large range and steady rain.
Show the answer
Cool temperate, because of the large range and steady rain.
Yes. A 14 degree range and steady rain all year match a place like London.