Download BOM WEB ACTIVITY weather and climate

Go to the web site: http://www.bom.gov.au/lam/weathed.shtml
1. What is the difference between weather and climate?
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2. What causes weather?
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Now go to the web site: http://www.bom.gov.au/info/weathmap/
3. What are the dominant features of weather maps?
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Television and newspapers also often carry forecast weather maps which indicate how the weather patterns are
expected to develop. Meteorologists use a wide range of information and techniques to formulate weather
forecasts. The weather map does not and cannot show all of these factors. It is a fairly simple representation of
past and probable future locations of surface weather systems (highs, lows, fronts, etc.). Nevertheless it provides
a useful guide to the weather.
4. Who benefits from better understanding of weather maps? Why?
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Go to the link What do weather maps show?
What do weather maps show?
The most obvious features of the media's weather maps (Figure 1 is an example) are the patterns of high and low
pressure, and the barbed lines identifying cold fronts.
FIGURE 1.
TYPICAL NEWSPAPER WEATHER MAP.
5. What way does air rotate around a low and high in the southern hemisphere?
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6. How is wind strength indicated on a synoptic chart in most cases? In what way do tropical meteorologists
indicate wind strength?
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7. What do shaded areas on a weather map represent?
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8. How is wind speed and direction shown on weather map?
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Now click on link back to start at the bottom of the page, Go to the link Hot or cold?
Hot or cold?
Remembering that air flows clockwise around low pressure systems and anticlockwise around high pressure
systems, this indicates a fairly typical summer weather map (Figure 2).
FIGURE 2. A SUMMER WEATHER MAP.
9. What do Northerly winds over eastern Australia carry in summer? What classic summer event do they carry?
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10. What do moist, easterly winds over eastern Australia carry in summer?
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The cold front passing South Australia replaces the hot, dry northwesterlies with southerlies carrying cooler,
often relatively humid air from waters south of the continent. Such summer fronts are often quite shallow and may
not penetrate far inland, particularly if they are distorted and slowed over the Victorian mountains.
In (Figure 3) a relatively common winter weather map shows:
FIGURE 3. A WINTER WEATHER MAP.
11. Very cold, unstable air from where will bring what type of temperatures and to which region?
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12. Examining both Figure 2 and Figure 3, what difference do you notice about Summer Synoptic charts
and Winter Synoptic charts?
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Now click on link back to start at the bottom of the page, Go to link Rain or Fine?
Rain or Fine?
13. What is a cold front? What type of weather do they bring to a region?
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14. What is a warm front?
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Now click on link back to start at the bottom of the page, Go to link How strong will winds be?
How strong will the winds be?
A mean sea level pressure chart shows the direct relationship between isobar spacing (pressure gradient) and
orientation, and the strength and direction of surface winds. The general rule is that winds are strongest where the
isobars are closest together. Thus the strongest winds are usually experienced near cold fronts, low pressure
systems and in westerly airstreams south of the continent. Winds are normally light near high pressure systems
where the isobars are widely spaced. However, because of a latitude effect winds in middle latitudes are lighter
than those in the tropics with similarlyspaced isobars.
15. Where are Australia’s most destructive winds generated from?
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16. What are tropical cyclones.
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The pressure gradient is very steep towards the cyclone's centre and wind speeds can be about 110 kilometres
per hour with gusts 50 per cent or more above this mean wind speed. When the cyclone has moved inland it is cut
off from its heat energy source, the ocean (it requires sea surface temperatures above 26.5 C), its intensity has
decreased and wind speeds have dropped.
Now click on link back to start at the bottom of the page, Go to Using weather charts link
Using weather charts
17. What factors are used in the preparation of weather charts?
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While predicted (prognostic) weather charts are essential to the forecast process, they must be interpreted by
meteorologists to prepare specific weather forecasts and warnings. Forecast errors still occur, due to limitations in
data or the forecast models, and the inherent complexity of the atmosphere, but forecast accuracy has increased
very significantly since the introduction of satellite information and mathematical modelling. Prognostic charts
shown routinely on television and in newspapers predict conditions up to three days ahead.
It will be realised by now that a single weather map is only a forecasting aid and that a great deal of other data
and information must be gathered and processed before a forecast is issued.
Now access the site: http://www.bom.gov.au/lam/climate/index.htm
Click on Climate of Australia tab
18. Why is there a seasonal fluctuation in temperature for Australia?
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Now click on Outline of Australian Climate Link
Australia's climate is dominated by the dry, sinking air of the subtropical high pressure belt which moves north and
south with the seasons. This causes the rainfall pattern over Australia to be strongly seasonal and helps to define
the main climate regions. Use the main seasonal zone rainfall map to complete the table showing summary of
rainfall zone and examples of cities in this zone.
Summer
Dominant
Summary of
Rainfall Type
City
Examples
Summer
Winter
Dominant
Winter
Uniform
Arid
Scroll down and complete the table showing major cities in Australia and their mean temperatures.
Location
Mean Temperatures (°C)
January
July
Max
Min
Max
Min
Rain
mm
Annual
Adelaide
Alice Springs
Brisbane
Canberra
Darwin
Hobart
Melbourne
Perth
Sydney
19. Using the above table, summarize the climatic conditions for Sydney and Alice Springs, why are they so very
different?
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20. Using the above table, summarize the climatic conditions for Perth and Hobart, why are they so very different?
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