WH1080 rain gauge versus graduated cylinder.

[beteljuice]

.. 10M up on the tower but with very little wind today 8-18mph ..

That my accuracy friend is a blatant contradiction in terms

[Repairman77]

.. 10M up on the tower but with very little wind today 8-18mph ..

That my accuracy friend is a blatant contradiction in terms

8-18mph is very little wind when you live out here in the open Fens of East Anglia.
Mike.

[steve]

18 mph is dead calm, actually

[Repairman77]

18 mph is dead calm, actually

Yes Steve, I don't call it windy here until it blows me off my pushbike.

Incidentally I've just finished my Rainfall measurements for the last two decades (since Nov. 1990); in PDF format which can be found here...
http://www.mjgoodall.co.uk/Rainfall-8.pdf
if anyone is interested in rainfall for Cambridgeshire UK.

Mike.

[aaardvaark]

Mike - I was wondering if you got it all worked out satisfactorily?

From reading this and my limited experience, I think your very low readings could be due to your dressmaker's net cover which sounds as though it would hang on to the water, as well as splash lots out.

Edit: as soon as I wrote this I found another thread that you discussed this. Wouldn't you be better attaching your mesh (coarse, like mosquito netting) under the funnel inlet i.e. inside the unit? Then there's nothing to interfere, hold on to the water or splash on the outside collecting area. I haven't done any spider proofing yet until I get basic calibration sorted.

Julian

[mcrossley]

However another problem came to mind; a large funnel would collect even more raindrops before they started falling into the hole, in very light rain conditions. Coating the funnel with the acrylic window cleaning stuff may help though.
Think this is a 'no win' situation.

I was wondering what the perceived wisdom was here? Use something like RainEx to make the stuff bead up and run off (problem it can collect a lot of small beads before they start 'rolling'), or make the surface 'wettable' so the water tends to collect at the bottom?

Or maybe go with the RainEx and have a 'Windy Miller' or rather 'Windy Woodpecker' that constantly taps the funnel to shake the drops down!

Mark

[beteljuice]

WD40 / Rocket or similar works wonders.

No matter what size your collection system there is always the viscosity / droplet run problem (or in hot weather evaporation !).

However; It can generally be said the larger your collection sytem the less overall (percentage-wise) error there will be.

Remember - In terms of 'measured' rain, meteorologically speaking, anything less (observed Vs. measurement) than 0.2mm / hr is "A trace of Rain".

You have to remember most weather measurements are actually trends and 'near enough' values.

[Gina]

Since adding a large steep sided funnel to my rain gauge I've seen a great improvement. My rain gauge is now responding as I would expect.

[Repairman77]

I think we are always going to have problems when trying to accurately record very small amounts of rain (under 1 or 2mm) no matter how many mods we make which is a pity. However I've found the remote unit quite accurate when we get 5mm or more in an hour or two.

I guess it's just an anomaly that we'll have to put up with, and we're striving for an accuracy that we're never going to achieve.

I still use the 172mm diameter funnel rain gauge that I made for accurate recording.

Mike.

[nking]

This is probably a very stupid question but, has anyone considered/tried reducing the volume of the bucket size in the rain gauge as opposed to increasing the catchment area with a funnel? For example, use a filler so that only 0.2mm or 0.1mm of rain is required to tip the bucket. I haven’t opened up the rain gauge to check it out but I imagine the size may make this an impractical option! Keyhole surgery I guess!!

[RCE]

I imagine the size may make this an impractical option! Keyhole surgery I guess!!

It is more a question of weight change, without enough difference in weight between full and empty buckets the tip may not occur.

[Gina]

Much easier just to put a bigger funnel over the original. Improved mine no end