Wonky device suspected in sunshine surge

00:17, Jan 15 2014
tdn sun stand
Frida Gardiner, 5, plays in the sun.

Questionable calibration on a sunshine measuring device could be the culprit that robs New Plymouth of its proud new position as second sunniest spot in the country.

Figures released by the National Institute of Water and Atmospheric Research last week showed the city recorded 2668 sunshine hours last year, beaten only by Whakatane. Last year followed another record-breaking 2433 hours of sunshine in 2012.

However, both years are under investigation as the city's spikes in sunshine hours have coincided with the adoption of an automated sunshine measurement machine in November 2011.

Before the adoption of the machine, sunshine in New Plymouth was recorded manually with 2176 hours of sunshine in 2010 and 2025 in 2011.

"It still might work out that New Plymouth is the second sunniest but it does strike us as a little unusual that sunshine jumps 20 per cent in two years with the change in a measuring device," Niwa scientist Mike Revell told the Taranaki Daily News yesterday. The automatic device is controlled by Metservice and replaces a manual sunshine reader which required a person to physically measure the amount of sunshine each day.

The new machine collects the data automatically and is theoretically more accurate than the manual measure.


However, Mr Revell said that was only true when the machine was calibrated properly. Steps were being taken to determine whether this was the case, he said.

It was natural for Niwa to be sceptical of the data because it coincided with the adoption of the new device and the 20 per cent increase in sunshine was well above the 5 per cent above normal recorded in Stratford and Taumarunui over the same period, he said.

But Metservice communications meteorologist Daniel Corbett said the device had been installed according to Niwa specifications.

"As far as I have been told it is completely to their requirements. Sunshine is recorded in the way they requested," he said.

"There may be some further discussion to fine tune it in the future."

The weather station at Stratford is run by Niwa but the Taumarunui data is compiled for Niwa by the Metservice, just as it does for New Plymouth.

Taranaki Daily News