record sunshine

[midgrove]

Blenheim had record annual sunshine in 2015 of 2814 hours. Over the last 10 years the previous record was 2792 hours in Whakatane in 2013. My question is: is this an all time record? and if so it certainly hasn't made the news yet.

[RWood]

It is a record. However, there are 2 types of recording at sites now: by EWS sensor (now the most common) and a diminishing number of cases of manual readings from Campbell-Stokes recorders. The 2 sets cannot satisfactorily be compared at present. The Blenheim result, and all the Whakatane ones from recent years, were EWS measurements. At most sites, new EWS values have been anywhere from about 100 to 450 hours per annum better than the previous manual ones. Blenheim itself showed little or no difference however until last year, whereas Whakatane "improved" by a very large amount from the outset. The highest annual total obtained from manual readings was 2711 hours at Nelson in 1931, and Blenheim's was 2686 hours. During the very dry period from about July 2000 to September 2001 Nelson Aero (manual) at one point had a 12-month total around the 2800 mark.

My opinion is that the issue of record values is "cloudy" at present. I am deeply sceptical of the notion that Whakatane EWS readings from 2007 to the present show it as sunny or sunnier than Blenheim or Nelson given that manual readings from various sites there in the period 1957-2002 had it 100-150 hours lower than Blenheim - and it topped the list only twice (1957 & 1979) in that era.

[jamie]

Why don't they swap the sensors between Nelson/Blenheim with the whakatane one. That will answer your question

[03Stormchaser]

Whakatane may not want to do that....

[RWood]

Whakatane may not want to do that....

Indeed so!

[TonyT]

Surely someone, somewhere has done a comparison of the readings from the newer sensors used on the AWSs and the older manual instruments?

[NZstorm]

If you consider the geography then I would say Marlborough should be sunnier than BOP.
I doubt many BOP people care much about the sunshine debate.

[TonyT]

Surely someone, somewhere has done a comparison of the readings from the newer sensors used on the AWSs and the older manual instruments?

Answering my own question:

http://link.springer.com/article/10.100 ... -z#/page-1

It appears that the electronic sensors are more sensitive to sunshine in the hour after sunrise and the hour before sunset. It also appears that the two types of instrument respond differently in different cloud conditions.

[RWood]

Surely someone, somewhere has done a comparison of the readings from the newer sensors used on the AWSs and the older manual instruments?

Answering my own question:

http://link.springer.com/article/10.100 ... -z#/page-1

It appears that the electronic sensors are more sensitive to sunshine in the hour after sunrise and the hour before sunset. It also appears that the two types of instrument respond differently in different cloud conditions.

I've read several reviews from the UK over the years - for them, the overall readings don't seem to differ very much at most sites. But for whatever reason, EWS values at NZ sites are generally far higher. Good examples of this can be found at e.g. Paraparaumu, Greymouth, Hokitika, Whakatane (of course), Ashburton, Balclutha, New Plymouth etc. In some cases the predecessor manual sites were probably deteriorating, but that's not sufficient to explain everything. Paraparaumu shows a large difference in the same physical location, for example.

In a few cases, eg Palmerston North, the new exposure is inferior to the old one and the EWS readings are the same or lower. I think a lot more analysis needs to be done.