I have been suspecting for some time that my AWS gauge has been
under-recording. I've been tracking it against the accurate gauge of
someone who lives five miles away (but I recognise that there are
substantial local differences in rainfall) and my garden centre bought
plastic rain gauge.

My AWS consistently seems to under-record by an at least 10%, perhaps
by as much as 20% - in line with your figures!

The AWS (a Davis Weather Monitor) seems to under-record most (if you
see what I mean) when it is windy or the rain is heavy. The AWS is in a
more exposed site. I know it's important to get the AWS tipping bucket
absolutely level and I fear my DIY skills weren't up to the accuracy
required.

So today (just before I saw this message in fact) I ordered an accurate
manual gauge. I worry a bit about changing recording systems, but it
has to be done.

Trevor
From a parched (but perhaps not quite as parched as he might have
thought) Dundee.


On 2009-05-04 11:05:03 +0100, Hugh Newbury said:

In late February 2009 I was lent a standard rain gauge. Up till then I
had always relied on the automatic weather station's tipping bucket
gauge to give the rainfall. But February brought snow, which was hard
for the AWS to cope with. So I got the standard rain gauge, which
managed, with some help from me in melting the snow it had gathered, to
give real figures.

Part of the deal for the loan of the rain gauge was that I should
compare the output of the AWS and the gauge. This revealed substantial
differences between the outputs, the AWS showing less precipitation than
the standard gauge. It occurred to me that it might be of interest to
others in the field of weather data collection to see the comparison I
have been making since the beginning of March 2009. For instance, the
March and April total figures a

AWS Std Rg Diff
March 52.2 70.85 -18.65
April 57.0 81.35 -14.35

For the daily figures, please go to my website (in sigfile below) and
click on 'Rain'.

I have changed my daily [WR]s from AWS to standard rain gauge figures,
but the 'Current' figures on my website are still from the AWS because
that's where the software gets its data.

Hugh