Sunshine Recorder

Holger · **Posted:** Fri Aug 05, 2011 9:38 pm

Good luck with the trial, Alan - hope it'll rattle the MO's cage a bit!
Holger

PaulMy · **Posted:** Sat Aug 06, 2011 2:20 am

Alan,
Is that something we can go to or see on an ongoing basis?

I now have a full month of data for July and we had some sun every day. All be it just a very small amount on the 28th. I had a computer glitch while I was not at home on the 21st and was not able to record for most of the day, but when I got back home salvaged recording a small amount of sun shine, and that was also the day we broke all of the all-time high records in Cumulus.

Paul

apenwith · **Posted:** Sat Aug 06, 2011 7:04 am

Hi Paul
I'm not sure yet when the Met Office will provide me with the data - it may well be at the end of the trial. I have been comparing the daily figures published by the same site for a while now and there is some quite close agreement to my figures but as the site is 12 miles away there are differences. For the trial our recorder is less than a metre away from their Kipp & Zonen pyrheliometer so we can exactly measure like with like.
Interestingly - speaking to the meteorologist at the site - he was of the opinion that there is no totally satisfactory algorithm for converting W/M2 to sunshine hours.
We have an algorithm on trial for converting our measurements to W/M2 but the accuracy is probably only about +/- 10% at present.
Regards
Alan

PaulMy · **Posted:** Sat Aug 27, 2011 5:10 am

Thanks Steve for adding the B/L option and showing Sunshine hours in latest beta :clap:

I notice this is logged in dayfile.txt, monLog.txt, and also in Realtime.txt as mentioned in Help. Unless I've missed it, any plans to add to Graph or Select-A-Graph and is this even possible? I did not notice it as a webtag, and extracting from those files to show on my website in some form is still beyond my ability.

Paul

apenwith · **Posted:** Sat Aug 27, 2011 7:17 am

Hi

Three weeks into the Met Office trial and a chance to compare the B/L sunshine with figures from another website (not the official figures - I will be getting those from the MO later). So far I am seeing a difference of 309 minutes in around 17000 minutes of recording. That's less than 2% difference - it could, of course, be that differences are cancelling out over the period but at first sight it looks promising. It won't be till I get the official hour by hour figures we will know for sure.

Regards
Alan

steve · **Posted:** Sat Aug 27, 2011 8:14 am

PaulMy wrote:

Unless I've missed it, any plans to add to Graph or Select-A-Graph and is this even possible?

Yes, I'll probably get around to plotting sunshine hours at some point.

apenwith · **Posted:** Wed Sep 21, 2011 7:54 am

Hi
We now have the Met Office data. There are some hourly differences which may be due to the MO method of averaging their readings but the daily figures show a close agreement. We would expect the B-L recorder to be slightly higher on some days as it can detect the sun from the horizon. The graphs show our initial findings. The time scale is 30 days starting on 5th August against minutes.
Regards
Alan

steve · **Posted:** Wed Sep 21, 2011 8:11 am

That looks impressive - you must be very pleased :clap:

RayProudfoot · **Posted:** Wed Sep 21, 2011 5:03 pm

Congratulations to you both. That's a great achievement given your resources compared to the big boys. :clap:

yv1hx · **Posted:** Thu Sep 22, 2011 12:42 am

A great success!! :clap:

Holger · **Posted:** Sat Sep 24, 2011 10:56 pm

Brilliant result - well done Alan & Ole!!! :clap:

Has anyone from MO commented on the trial yet?
I am as pleased as punch with my recorder and can only recommend it!
Holger

PaulMy · **Posted:** Sun Sep 25, 2011 2:44 am

Very impressive comparison. Alan and Ole, you've done a wonderful job with your ideas and must feel very satisfied to have those results from an official source. I am very happy with the data I am seeing from my B-L installation, and so surprised with the number of days and hours of sunshine we have had this summer.
Paul

apenwith · **Posted:** Sun Sep 25, 2011 9:41 am

Hi all

Looking at the graphs posted earlier there are some differences at an hourly level between the MO data and ours.

These could, in part, be explained by the methods used by each device for calculating the sun ON situation. The B-L recorder checks for sunshine every second whereas the MO system uses a method that checks the average radiation of 30 readings at 2 second intervals. This means that if the sun is shown to be just above the threshold for a period followed by low radiation readings the average could decide that the sun was OFF for that minute whereas the B-L recorder would have logged the ON period. Similarly a period of high radiation could tip the MO average to an ON minute although the sun may have been visible for a short time only.

Obviously this effect would be more pronounced with fast moving fairly small clouds so we would expect any difference to be greater on days with rather less sunshine recorded.

It could be said that we are producing figures which are more accurate than the official data - as we have said before - we are comparable to the man in his deck chair with a stopwatch who just knows if the sun is shining or not.

We are, however, looking at a modification to the recorder which should enable us to use the WMO threshold as the sun ON decision point as well as producing fairly accurate W/M-2 readings.

Regards
Alan

gemini06720 · **Posted:** Sun Sep 25, 2011 11:01 am

apenwith wrote:

...We are, however, looking at a modification to the recorder which should enable us to use the WMO threshold as the sun ON decision point as well as producing fairly accurate W/M-2 readings.

Alan, I do hope you (and Ole) will keep (or make) both options available, the original B-L 'check for sunshine every second' option and the MO 'checks the average radiation of 30 readings at 2 second intervals' option...

Just because the MO instruments use a different measuring method does not mean that it is the 'right' one... :roll:

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