Practical: Finding the daily and yearly air-temperature range
Air temperature changes through the day and through the year. In a day it is usually highest around 14:00–15:00 and lowest just before dawn. To draw a graph, put time on the horizontal axis and temperature on the vertical axis, mark each reading with a dot and join the dots. The temperature range (amplitude) is the difference between the highest and lowest temperatures: range = highest − lowest. The difference within a day is the daily range, and the difference over a year (between the mean temperatures of the warmest and coldest months) is the annual range. When subtracting a negative number put it in brackets: 28 − (−3) = 31. A small range means a mild climate (near the sea); a large range means a sharp one (far from the sea, in deserts).
Practical: on squared paper draw axes (time horizontal, temperature vertical; 1 square = 2 °C). Plot the 4 readings you collected in the last lesson, join them and find the daily range. If you have no readings, use the table 6:00 –1, 9:00 +3, 12:00 +9, 15:00 +14, 18:00 +7, 21:00 +2 °C. Safety: use a soft pencil rather than sharp tools; when measuring outdoors, never look at the Sun.