Just Three Little Clicks…

and the rain gauge at Tawa Weather will have recorded an astonishing 1.2 metres of rain for 2006.

The mechanical rain gauge contains a pair of tiny buckets perched atop a small see-saw device. When it’s raining, moisture enters the funnel-shaped collector above and runs down and through a small nozzle and into the active rain bucket. As the bucket fills to its capacity of 1 mm, the see-saw tips and the other bucket is placed below the collector nozzle while the measured rain drains out through the bottom of the gauge.

The see-saw (more accurately called a rocker) triggers a pulse to the weather station when it changes over, and the weather station adds 1 mm of rain to its display as well as notifying the rain count on the serial port to the weather server.

The weather server, which currently runs Weather Display software, receives data on rain, wind, temperature, humidity and air pressure from the weather station every four seconds or so. This information is used to calculate the current weather conditions, update historical information and display the data in a graphical format.

The rain gauge has to be a hardy beastie because it sits on a platform on a mast away from overhanging trees which could cause water to trickle into it, and away from structures that might stop it measuring rainfall accurately during windy conditions.

The gauge’s isolation makes it an attractive place for a bird’s nest and a snug hidey-hole for spiders with a hermit mentality. The first sign of a problem is usually the absence of rain information on the weather station’s webpage following a heavy downpour. Over the years, weather station owners have had to shinny up their masts periodically to wrestle with grumpy arachnids which had set up home in the rain gauge and wedged an old newspaper under the rocker which was keeping them awake with its clattering, much as we might wedge a rattling window with a piece of card.

Non-paying tenant birds are usually more obvious, as they can be seen promenading on the deck of their new home, holding barbecues on fine evenings. However, birds and leaves can be discouraged from blocking the collector bucket by a unique modification to the WM 918 rain gauge developed in the high tech laboratory of Mana Weather.

The rain gauge comes with a dome-shaped net supplied by the doyen of hair-netters Ena Sharples. For best results, the net (I’ve named mine Ena in her memory) should be installed dome-up so that any leaves which stick temporarily will be blown off when they dry out, and any birds who want to set up a home with stunning views find that their beds fall off and go clonk on the ground below.

But the exposed dome can be buffeted by Wellington’s gentle zephyrs, so it is best to lock it in place with a self tapping screw which can be withdrawn when maintenance is required.

With this precaution in place, the rain gauge requires less maintenance, and owners who suffer from vertigo can enjoy a life of sloth. But complacency is a dangerous thing, especially when a new record is about to be set – is the beast working correctly?

But this sloth is not about to clamber up to make sure that the rain gauge is in the peak of health and ready to count those crucial 3 mm of rain. There’s a cold southerly blowing and the rain is a bit chilling.

And I’ve got to go out, anyway. I have an appointment with my plastic surgeon – he’s measuring me for a set of webbed feet so that I can enjoy the outdoors during “summer”. Now, where did I put my water-wings?…

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