Month Jan Feb Mar Apr may June July Aug Sept Oct Nov Dec Rainfall in mm 18 17 20 39 48 90 112 90 56 47 30 25 Temp in ºC 21 21 20 17 15 12 12 13 14 18 18 20 ...

Answer Details

(a) Combined rainfall and temperature graph for Station X

The two elements are drawn on the same base line of months but on two different vertical scales: rainfall is shown as columns read against the left-hand scale (in millimetres) and temperature is shown as a smooth line read against the right-hand scale (in degrees Celsius). The paired figures used are:

Month	J	F	M	A	M	J	J	A	S	O	N	D
Rainfall (mm)	18	17	20	39	48	90	112	90	56	47	30	25
Temp (ºC)	21	21	20	17	15	12	12	13	14	18	18	20

(b) Calculations

(i) Annual temperature range

The annual temperature range is the difference between the highest and the lowest mean monthly temperatures.

Highest temperature = 21ºC (January and February)
Lowest temperature = 12ºC (June and July)

\[\text{Range}=21^{\circ}\text{C}-12^{\circ}\text{C}=9^{\circ}\text{C}\]

(ii) Mean annual temperature

Add the twelve monthly temperatures and divide by 12.

\[\text{Sum}=21+21+20+17+15+12+12+13+14+18+18+20=201^{\circ}\text{C}\]\[\text{Mean}=\frac{201}{12}=16.75^{\circ}\text{C}\approx 16.8^{\circ}\text{C}\]

(c) Climatic type

The station shows the following features:

• Warm, moderate temperatures throughout the year (range only 9ºC, mean about 16.8ºC), so there is no true cold season.
• Highest temperatures occur in December, January and February (about 20–21ºC) and the lowest in June and July (12ºC). Since summer falls in December–February, the station lies in the Southern Hemisphere.
• The rain comes mainly in the low-sun (winter) season, June–August, reaching a maximum of 112 mm in July, while the high-sun (summer) months of January–February are the driest (17–18 mm). Total annual rainfall is 592 mm.

Warm dry summers combined with mild wet winters and a small temperature range identify the station as a Mediterranean climate (also called the Warm Temperate Western Margin climate), such as that experienced around Cape Town, Perth or central Chile.