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230 SCIPAD - BIG IDEAS - BOOK 2
EARTH SYSTEMS
1. What is a ‘rain shadow’?
2. Define the term ‘predominant’.
3. What is the predominant wind direction in New Zealand?
4. If the predominant wind direction was from the east, state which town (Hokitika or
Christchurch) would experience the rain shadow.
5. Outline the processes occurring at :
1
2
3
4
6. New Zealand’s climate and weather is studied by a government agency called the
National Institute of Water and Atmospheric Research (NIWA). One of their responsibilities
is to monitor and collect rainfall data throughout New Zealand. The table below shows the
rainfall data they have gathered for Hokitika and Christchurch.
Hokitika Christchurch
LOCATION JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Hokitika 250 172 217 249 245 233 232 224 250 286 240 278
Christchurch 42 39 54 54 56 66 79 69 47 53 44 49
Average Monthly Rainfall (mm) for the Period 1971-2022
(a) Calculate the total mean annual rainfall for: (i) Hokitika:
(ii) Christchurch:
(b) Use the data to plot a graph of the average monthly rainfall on the graph paper
provided on the next page.
East
1
2
3
4
Southern
Alps
The Water Cycle’s Effect on Climate - Rain Shadows
A rain shadow is an area of land that gets reduced rainfall because it lies behind a mountain. In
New Zealand there are a number of regions that experience rain shadows, particularly the east
coast of the South Island.
The predominant (most frequent) wind direction in New Zealand is a westerly wind (a wind that
comes from the west). This warm, moist air blows in from the Tasman Sea and rises as it gets pushed
up over the Southern Alps. The temperature falls as the air gets pushed higher. This causes the
moisture in the air to condense and precipitate (rain/snow) on the western side of the alps. The
dry air descends down the eastern side causing the eastern side of the Southern Alps to be drier
than the west coast - creating a rain shadow.
West
Christchurch
Hokitika
