Humble box protects vital bureau technology

Malcolm Riley.
Malcolm Riley.

IT doesn't look much: a louvred white box sticking a bit more than a metre from the ground next to a sewerage plant at Invermay.

But it's thanks to the Bureau of Meteorology's Stevenson screen that Launceston residents know the exact temperature in their region.

That's not to say they always agree.

Bureau spokesman Malcolm Riley said people regularly disputed the organisation's temperature readings. "Our instruments record temperature differently to how you feel," Mr Riley said.

While wind, shade or heat- exuding surrounds can affect the way people experience the heat, the well-designed Stevenson screen shields temperature-measuring devices to ensure its readings are accurate.

Nothing is accidental in its design. White reflects heat, the louvres allow for air to flow through the device and the double roof shields the box from the sun.

The screen's height - 1.2 metres - is the average chest height for humans internationally. Situated at Ti Tree Bend, its location allows for readings of the Launceston area. Mr Riley said placing the screen in a more central site, such as the bitumen-heavy city, would affect the ability of the instruments to accurately read and record temperatures.

"It's quite a good station because we like stations that are left alone and this is ideal," Mr Riley said.

Inside the Stevenson screen are two sensors. Each resistor gives a wet or dry bulb temperature respectively, allowing for predictions on fog and dew.

The sensors send an electronic reading every minute, allowing for it to flow through one of about ten computer models to find the day's most accurate temperature.

The Stevenson screen design is more than 100 years old.

"Travel the world and you'll see one somewhere," Mr Reilly said.


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