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9.8 Option - Disasters: 2. Technological developments and weather patterns
Extract from Senior Science Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW.
[Edit: 26 May 09]
Prior learning:
Preliminary course: 8.5 The local environment
Science Stages 4-5 .4.1c), 4/5.1e), 4.9.3, 4.9.4 , 4.9.5, 4.9.6, 4.10 d), 5.9.2 a), 5.9.4 f).
define the term 'atmospheric pressure' and describe the movement of air currents between areas of high and low pressure
- Atmospheric pressure is the force per unit area due to the weight of the atmosphere (a layer of gases). These gases are kept in place by the force of gravity. The pressure of the atmosphere is measured in hectoPascals. (1 hectoPascal = 100 Pascals. 1 Pascal is a unit of pressure equal to one Newton per square metre)
- Air moves from a place with high air pressure to a place with low air pressure. This movement of air is what we notice as a breeze or wind.
- Typically, the air pressure varies from about 980 hPa to 1100 hPa.
- On a weather map, the air pressure in different places is shown by lines, called isobars, drawn through points with the same air pressure.
plan, choose equipment or resources for and perform a first-hand investigation to gather available evidence to demonstrate the effect of differences in air pressure
- The class could brainstorm to come up with ideas about an investigation to demonstrate the effect of differences in air pressure. Consider what equipment is available. When you have decided on some ideas discuss them with your teacher.
- When you have decided what to do, plan how you will do the investigation, including choosing what equipment you will use.
- Perform the investigation.
Two possible investigations are given below.
- Fill a balloon with air, but do not tie it off. Fill a length of clear plastic tube with water. Shape into a U form. Now attach the balloon to one end of the plastic tube, making sure no air escapes. Release the air from the balloon so it can push up the column of water. Record the difference in heights of the water columns. This height difference is a measure of the pressure of the air in the balloon. Repeat this by blowing up the balloon to different sizes. Make a general statement about the height of water column that different air pressures can support.
- Blow up a balloon but do not tie it off. Collect a freezer bag and connect it to a tube or hose using adhesive tape, making sure that you have made an airtight seal. In which container is the air at greater pressure? Connect the balloon and the freezer bag with a hose, making sure that no air can escape. Release the air from the balloon. Does the balloon empty itself completely? If it does not, explain what makes the movement of air stop. In which direction did the air first flow? How can you control the flow of air?
High and
Low Pressure Systems 
This information is meant for younger students but it explains
pressure systems well.
identify that the distance between isobars on a weather map indicates the relative amount of atmospheric pressure in an area
- If the isobars are close together, this means that places that are not far apart experience a large difference in air pressure. As a result, the winds in this region will be strong.
- If the isobars are a long way away from each other, this means that the difference in air pressure between two places is not very large. As a result, the winds will be quite gentle.
This is very similar to a map showing contour lines. A contour line joins points which have the same height above sea level. If you have contours close together, you have a steep hill and you would roll down it quite fast. If the contours are far apart, then you have a gently sloping hill. You would roll down this hill more slowly.
gather secondary information and use the available evidence to compare changes in the relative air pressure in an area over time and relate changes to changing weather patterns
- You could gather secondary information by collecting weather maps from the newspapers over a number of days. Alternatively, you may go to the Bureau of Meteorology website over a number of days to collect air pressure data for a number of locations in New South Wales.
- If you have used the
website record these data on a number of maps of the state or print the information
from the website. If you didn't print them use these data to draw isobars
on your map. Then use the isobars to predict the strength and direction of
the winds produced by the air pressure differences. The Bureau of Meteorology
has a website for students and teachers to explain air pressure.
High and Low Pressure Systems Bureau of Meteorology , Melbourne, Australia - Relate the weather changes to changing air pressure differences.
describe the relative pressures involved in the formation of tropical cyclones and tornadoes
- Cyclones and tornadoes are examples of extremely violent storms produced by large differences in air pressure. They are also known as typhoons or hurricanes, depending on where you live.
- The factors they have
in common are:
- they are formed when an area experiences extremely low air pressure
- they are produced by extreme differences in air pressure
- they often form over water and then move on to land
perform an investigation using second-hand data and use the available evidence to trace the movement of a tropical cyclone
- Perform the investigation
by using a CD ROM, the Internet, text books or an encyclopedia to find examples
of a tropical cyclone. Then report on this cyclone by describing:
- when it occurred
- where it occurred
- the path the cyclone followed - it could be plotted on a map
- the damage and injuries that were attributed to the cyclone.
A good website for
Cyclone Larry is the Bureau of Meteorology, Queensland
describe technological advances that have contributed to increased understanding of meteorology
- Meteorology is the study
of the weather and climate. There are several major aspects to it:
- Measuring the characteristics of the weather
- Predicting the weather
- Researching ways to improve the measurement methods.
- We take weather forecasts for granted. Every newspaper has a forecast in it and every news bulletin has a small segment devoted to it. This is because so many people rely on the weather to some extent. If you are a farmer, a fisher who goes to sea, a bushwalker or cross country skier or a pilot, then knowing what weather to expect is essential.
- To predict the weather, meteorologists need to measure quantities like air pressure, humidity, temperature and wind speed and direction. These measurements have to be carried out not just in one place, but over the whole country. We cannot measure these properties in all places, so they are measured in as many places as possible, as often as possible. Normally a person is needed to make any measurement. That would require a huge number of people waiting around all day to make and record measurements. These measurements then have to be interpreted to make predictions about the weather.
- To predict the weather
you have to measure its characteristics
- in many places, all over the country, at ground level and high up in the air
- as often as possible.
- The basic tools for measuring
these characteristics include:
- thermometer for temperature
- barometer for air pressure
- anemometer for wind speed
- hygrometer (or wet and dry bulb thermometer) for humidity.
- The methods for measuring
characteristics of the weather (and their accuracy) have improved thanks to
electronics and computers
- Datalogging equipment allows unstaffed stations to carry out measurements at regular intervals 24 hours per day. This data can then be retrieved when needed. As a result, 'weather stations' may be placed in the most inhospitable places and left to record information without a person to run it.
- The measuring equipment has become more reliable and accurate thanks to different sensors that can be connected to datalogging equipment.
- Satellites orbit the Earth and make measurements of the atmosphere. This includes simply taking photographs to show cloud movement as well as remote sensing technology to measure other characteristics of the atmosphere.
describe the relationship between the monitoring of weather patterns by radar and laser light and the analysis of reflected wave patterns by computers
- NASA
scientists are using high frequency radar to monitor the strength and direction
of the Earth's winds. Light Detection and Ranging (LIDAR) technology beams
laser light through the atmosphere, which is reflected by dust and fine particles
(aerosols). The elapsed time between the sending and reflection, indicates
the distance to a given dust particle, whilst the associated colour shift
indicates the particle's velocity.
- Radar excels at piercing bad weather, but it needs raindrops, hail or snow to get a signal. LIDAR struggles to go through thick clouds or heavy rain, but it can get you wind (measurements) in clear air, because it relies on aerosols.
- From the collection of this data, wind speed and direction can be determined over large areas.
- LIDAR is similar to the
Doppler Radar technology currently used for wind speed determination, however
it uses higher frequency electromagnetic waves (light). LIDAR's higher frequency
radiation will be reflected by smaller particles than lower frequency radiation
(microwaves) of radar, allowing it to determine wind characteristics in clear
conditions. (Adapted from The Lab, ABC Science Online)
More information can be obtained from FirstScience.com.
explain why satellite photographs of cloud patterns have improved the reliability of interpretations of weather regularities and knowledge of global weather patterns
- Full-earth images of satellites help Australian weather forecasters trace the life cycle of weather systems, particularly those approaching from surrounding oceans. Satellites provide Australian forecasters with better data about air pressure, cloud patterns and solar radiation estimates.
- A Japanese-built satellite, MTSAT-1R,is now snapping hourly photographs of weather fronts in the Asia-Pacific region and is beaming them down to a base station at Cribb Point, near Hastings in Victoria.
Further Activities
- Take a tennis ball and squeeze it. Try to flatten it. Can you make it completely flat? Describe and explain your observations. Now compare your observations with those you would get if you tried the same with a cricket ball. Which property of matter makes you get different results for the different balls?
- Build (or obtain) a 'wind machine'. What effect does heat have on air? Light the candle in the smoke machine and hold a source of smoke above the inlet pipe as shown in the instructions. Observe the motion of the smoke and explain your observations. Use this model to explain how winds are caused, making sure you identify the source of heat that causes the movement of the air across the surface of the Earth.
- Build a 'cyclone machine' [Two 1.25L soft drink bottles, one of them half filled with water and then stuck neck-to-neck with 'electrician's tape' or other means] Turn the bottles upside down, to make the water flow from one bottle to the other. What do you notice about the direction in which the water flows from one to the other? Does it dribble down or spiral down?
- Collect weather maps from a daily newspaper. Copy the symbols used on the maps and summarise them and their meanings in a table in your book.
- On one weather map, use the location and spacing of the isobars to predict the direction and speed of the wind in a given area. Find out whether the weather forecast published in the paper agrees with you.
- Keep a diary to record the weather predictions made by the Bureau of Meteorology (and published in the papers or on the news at night) and the actual weather conditions on the day for one week. For what percentage of the time were the predictions correct?
- On a map of New South Wales, draw the locations of all the places for which a weather report was produced. Where do you find most 'weather reporting stations'? Can you explain why this is so?
- Find out what is meant by 'relative humidity'. Obtain a 'wet and dry bulb' thermometer. Use it to calculate the relative humidity in the room, and outside. Suggest factors that may increase or decrease the humidity at a given time.
- Find out what each of
the following terms means when we talk about the weather:
- maximum and minimum temperature
- average temperature
- average rainfall
- fine, overcast, cloudy, rain, showers.
- Use a CD-ROM, encyclopedia or other book, or the Internet to look up the Beaufort scale used for measuring wind strength. In particular, find out what observations need to be made to record and/or report wind strength. Which is a better term to use, wind speed or wind strength? Explain your answer.
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