NIWA environmental technician Ralph Dickson checks the electronic sunshine recorder at the A & P Showgrounds in Richmond on Monday. Photo: Simon Bloomberg

Sun crown ‘shady’

Richmond’s sunshine hours win clouded by science

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Nelson City may have finished well behind Richmond in the race for the title of New Zealand’s sunniest centre in 2016 year but meteorologists have shed some light on the situation which indicates those results are just a little bit shady.
Richmond was crowned the country’s sunniest centre last week when NIWA figures showed that the town had recorded 2840 hours of sunshine. Blenheim was second on 2582 hours with Takaka third on 2534 and New Plymouth fourth on 2503.
Nelson City slipped off the pace, recording just 2491 sunshine hours last year after topping the sunshine stats five times and finishing second three times in the last 14 years.
But the Nelson weather forecaster John Matheson says the results are shady and the big discrepancy between Nelson and Richmond sunshine hours was a direct consequence of the different equipment used to record the data.
John, who is one of the region’s most experienced weather experts, says the Nelson Airport weather station has a “trusty old” Campbell Stokes sunshine recorder which only records direct sunshine in clear skies. In contrast, Richmond’s weather station at the A & P Showgrounds uses a modern electronic sunshine recorder which records radiation from both clear and cloudy skies and overestimates the sunshine hours.
John says it’s “inconceivable” that there was 400 hours difference in sunshine hours in 2016 between the two weather stations that are just four kilometres apart. He’s also amazed that Richmond claimed the national record for sunshine hours when the Nelson-Tasman region experienced above average rainfall for 2016.
“Nelson recorded close to average sunshine during 2016, which would be commensurate with such a high annual rainfall,” he says.
“How a station (Richmond) so close could then claim a New Zealand record in sunshine defies logic.
“I don’t accept the Richmond result as a correct representation of our sunshine status during 2016. The reality is that these two different recorders are poles apart… the fudging of data for this element represents a grave step backwards in the measurement of our sunshine which historically has always been of bright sunshine, not ambient sunshine plus bright sunshine combined.”
Although the new electronic sunshine meters were tested in France against the older Campbell-Stokes machines, John says the setting needs to be adjusted for the clearer atmospheric conditions in New Zealand.
“There is really no other logical explanation, other than the new meters are simply over-doing the daily sun record,” John says.
NIWA’s environmental technician Ralph Dickson says it’s unknown why the Nelson and Richmond sunshine records are so different but concedes that it’s “probably instrumental”. Ralph says the “new electronic sunshine recorders are the future” and NIWA is working on calibrating the new recorders against the Campbell-Stokes to ensure historical data can be compared.

Tasman district mayor Richard Kempthorne celebrating Richmond’s sun crown last week. Photo: Andrew Board.
Tasman district mayor Richard Kempthorne celebrating Richmond’s sun crown last week. Photo: Andrew Board.

Politicians have also entered the debate with Nelson mayor Rachel Reese saying it’s time Nelson City updated its Campbell-Stokes recorder to be on a level playing field with Richmond, Whakatane, Blenheim and New Plymouth which all use the new electronic ones. Whakatane won the sunshine hours race in 2014 while Blenheim won in 2015.
“It’s great to see the wider Nelson-Tasman region recognised as the sunniest place in the country,” Rachel says. “But I’ve spoken to our weather expert John Matheson and he says there’s no way the sunshine hours are different between Nelson and Richmond. John says it’s just the difference between the sunshine recorders at Nelson and Richmond. We have a very old recorder so I think we’ll have to look at updating it.”
The Campbell-Stokes sunshine recorder was invented by John Francis Campbell in 1853 and modified by Sir George Stokes in 1879, and is one of the oldest and simplest meteorological devices that’s still in use today. It consists of a small glass sphere that focuses the sun’s rays onto calibrated paper, resulting in a burn line that can be measured.
Tasman mayor Richard Kempthorne acknowledges that the new technology may have played a hand in Richmond outshining Nelson, but says he’s happy to take the win.
“I’ll leave that debate on the technology to the scientists because they are the experts,” Richard says. “We have a stunning place to live and visit and the weather is a big part of that. It’s certainly what we are seeing this summer with so many visitors coming to our regions and all having a great time.”