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Understanding the Weather
How is the UV index measured?
The UV index is measured using two methods.
The first method measures the amount of energy contained in the UV radiation reaching the surface. This method expresses energy in milliwatts per square metre. The UV index you see on your TV news bulletins is based on this method.
The second method is based on the response of human skin to UV radiation. This was devised to standardize UV radiation reporting around the world. It is often used as a prediction. The index is determined for the time at which UV intensity is at its peak. This is usually around noon. It takes into account cloud cover.
UV Index values of less than 3 are termed “moderate” and will result in sunburn after one hour exposed to the sun. Index values between 3 and 6 are termed “high” and will lead to sunburn after approximately 30 minutes in the sun. Values between 6 and 10 are termed “very high” and will lead to sunburn after approximately 10 minutes in the sun. Values greater than 10 are termed “extreme” and will lead to sunburn in less than 5 minutes exposed to the sun.
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- Where do the background maps come from in your charts and how is the data turned into graphics?
- Who gives you the information used in your weather charts?
- What does wind chill mean?
- What is relative humidity?
- What is feels like temperature?
- How are sunrise and sunset times measured?
- How do I set my barometer?
- How is rain measured? How is snow measured? How do you calculate the water equivalent of snow?
- What are common sources of errors in measuring precipitation?
- What is the dew point?
- Why is wind not always included in the forecast?
- When you talk of a north or northerly wind, do you mean that the wind blows from the north or towards the north? Is this the geographic north of the magnetic north?
- How is a weather forecast made?
- What is the difference between a tropical cyclone, a hurricane and a typhoon?
- Do you have an explanation of the terminology you use in weather forecasts?
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Generation gone with the wind
13:20 AEST A weeklong stretch of low wind power was broken on Wednesday evening, as a weak cold front marched across southern Australia. The chart below shows that the National Electricity Market (NEM) has endured a weeklong stretch of low wind generation, with wind power providing around 6% of the NEM’s electricity, down from last year’s average of 13.1% (Mon, April 15 to Wed, April 17).
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