Hi

In January this year I was able to purchase a Solar Radiation Sensor
for my Davis VP2 station. Since then I have struggled to make some of
the calculations required for the COL Report titled "Global Solar
irradiation on a horizontal surface" ( Page 27 last month).

I can manage The Daily Mean, Max Daily and Min Daily but I dont see
how I can calculate the 1hr Maximum Value which you asked to quote a
1hr Maximum commencing on the hour ?

I am using the Weatherlink Reporter Software to produce the data . It
quotes for example 1259 w/sqm on the 21st June as the highest reading,
but on investigation with by minute by minute data on Weatherlink
itself, this lasted for only 10mins before it dropped. Are COL looking
for a 60minute high mean or just the highest figure. If its a 60mean
highest mean with my limited mathematical knowledge I cant see how to
work it out easily without trawling through 30days of data recorded at
1min intervals.

many thanks
Paul C
Brampton, Cumbria
www.bramptonweather.co.uk

On 7 July, 20:19, Paul Crabtree wrote:
Hi

In January this year I was able to purchase a Solar Radiation Sensor
for my Davis VP2 station. Since then I have struggled to make some of
the calculations required for the COL Report titled "Global Solar
irradiation on a horizontal surface" ( Page 27 last month).

I can manage The Daily Mean, Max Daily and Min Daily but I dont see
how I can calculate the 1hr Maximum Value *which you asked to quote a
1hr Maximum commencing on the hour ?

I am using the Weatherlink Reporter Software to produce the data . It
quotes for example 1259 w/sqm on the 21st June as the highest reading,
but on investigation with by minute by minute data on Weatherlink
itself, this lasted for only 10mins before it dropped. Are COL looking
for a 60minute high mean or just the highest figure. If its a 60mean
highest mean with my limited mathematical knowledge I cant see how to
work it out easily without trawling through 30days of data recorded at
1min intervals.

many thanks
Paul C
Brampton, Cumbriawww.bramptonweather.co.uk

Paul, it's the highest of the hourly means of global solar radiation
starting on an exact hour.

To determine this you'll need either a full set of hourly means
(straightforward enough with Excel's pivot table feature), or again
using a spreadsheet it's easy enough to work out 60 min running means
starting at any observation, then filter for the highest value
commencing at an exact hour. The highest in any month will almost
always be an hour commencing 1100 or 1200z for obvious reasons, which
also cuts down the number of cells to examine.

(If you don't use a spreadsheet to store/analyse your AWS data, then
maybe ask John Dann very nicely if he will look into adding the
function on the next release ... )

Short-period values will normally be much higher than the highest
hourly mean. For example, in June my highest 1 sec value was 1350 W/m2
(19 June), highest 1 min mean 1241 W/m2 (on 10 June), but the highest
hourly was 'only' 886 W/m2 (on 4 June), so quoting the highest 'spot'
value over a few minutes won't be comparable with other records.

Solar radiation is one of the most interesting of parameters to
record, particularly on showery days in midsummer like yesterday and
today down here when the intensity of insolation can vary by a factor
of 250 within a few minutes. I'm surprised more people don't measure
this element.

HTH.

--
Stephen Burt
Stratfield Mortimer, Berkshire

Stephen

Thanks for the reply. I dont currently use Excel to analyse my data,
the obvious question now is " How do I do that" ?

Hopefully John will pick up on the message and be able to help regards
his software which is producing reliable bright sunshine hour readings
comparable with my old sunshine recorder.

regards

Paul

On Wed, 8 Jul 2009 00:28:00 -0700 (PDT), Paul Crabtree
wrote:

Hopefully John will pick up on the message and be able to help regards
his software which is producing reliable bright sunshine hour readings
comparable with my old sunshine recorder.

Yes indeed I've just seen this.

Please remember that WLR** is currently still in beta - the version
available at present is intended more as a demonstrator of what the
program can do than as a polished final product with all the
calculated values properly validated. There still are at least a
couple of significant bugs to iron out in the calculations so I would
caution against using the results for any formal archival purposes for
the time being, though in general they should provide reasonable
provisional indications of final values.

I'm sorry that this beta state for WLR has lasted much longer than I'd
planned - it's really just a question of how much time I get to work
on background projects like this and the answer is not much recently.
Unfortunately as most part-time programmers will testify, program
development is not something that's easily done with an hour here and
an hour there - you really need a solid block of time, eg a week or
two of dedicated time, to remember where you'd got to with a program
and then make some further progress.

I've got one other major project that I'm currently working on, but
when that's done - maybe September time - then I'll aim to make WLR
the next priority and really look to make a properly validated version
available. And certainly, to answer the original point, if there are
any further parameters that can be readily calculated and included
then I'll be happy to do so. (But they need to be parameters likely to
be of general interest and/or eg in the COL specification and not
highly specialist or idiosyncratic ones - I don't want to add items
unlikely to be of wider interest to what is already a fairly long
parameter list and hence make life more confusing for the average
user.) I think what I'll aim to do is to release a new beta version in
the autumn and then invite any comments/suggestions for any extra
parameters or features that user might like to see.

**For anyone wondering what this is all about: WLR is a program called
Weatherlink Reporter which can read the monthly archive files that the
Davis VP/VP2 weather stations produce and can then generate very
flexible and comprehensive monthly reports from that data, including
the option of output in PDF format.

John Dann
www.weatherstations.co.uk