On 3 Jul, 08:53, "Philip Eden" philipATweatherHYPHENukDOTcom wrote:
"Dave Cornwell" wrote :

Philip, do you know what the lowest official rainfall figure was for
England. I have a chance of beating it!

Dave ... 57mm at St James's Park in London. If you are using
a rain-gauge which is not sited on the ground you should be aware
that you are probably losing a proportion of your rainfall, perhaps
up to 10%. I always recommend AWS users to have a manual
rain-gauge as well, at least for a year or two, so you can see the
relationship between the AWS's rainfall and the standard.

And dare I say there's also the question of calibration of the gauge
mechanism. Easy enough to do: many TBRs as shipped can be found to
under-read by 15-30% regardless of exposure, so worth checking.
There's also the fact that if it's a 1 mm tip you'll lose a lot more
through evaporation than a 0.2 mm capacity tipping-bucket gauge,
particualrly on days with small amounts which will often be lost
altogether.

My (calibrated) £25 wireless 1 mm unit reads typically 10-20% below my
standard checkgauge, my two 0.2 mm TBRs - admittedly much more
expensive units - are normally within 2%.

For instance, last month:

Standard checkgauge - 86.3 mm (= 100%)
TBR 0.2 mm tip - 87.7 mm (102%)
Wireless 1 mm unit - 78 mm (90%)

Stephen
Stratfield Mortimer, Berkshire