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