I see in some posts people record to the 0.1 of a millimeter. I currently just have the gauge that came with the WM-918 but today we had moisture but I recorded nothing
I did check it a couple of months ago and cleaned any spiders from inside it.
Should I be looking for a specialised gauge to run in conjuction with my WM-918?
Your thoughts?
There is no such thing as bad weather, just the wrong clothes.
I think some people have increased the catchment area of the gauge and divide the reading by the ratio increased catchment area...
eg increase the size of the top of the rain gauge by 10 times (big funnel or something) the resolution of the gauge is 10 times greater, so insead of the bucket tipping for every mm, it tips for 0.1 mm.
Software re-calibrated to read 1 bucket tip = 0.1mm
Fujita Phil wrote:What sort of rain gauges are we using out there?
I see in some posts people record to the 0.1 of a millimeter. I currently just have the gauge that came with the WM-918 but today we had moisture but I recorded nothing
I did check it a couple of months ago and cleaned any spiders from inside it.
Should I be looking for a specialised gauge to run in conjuction with my WM-918?
Your thoughts?
Hey Phil,
We had the same questions so I scattered a few "manual" (graduated plastic cup-type) gauges around the place and found that they always tallied precisely with the WM-918 electronic gauge. Various people have been telling me for ages that the WM-918 was under-reading, but it seems as if the old adage is correct, and people really do grossly overestimate the amount of rain which has fallen.
Of course if you try the same experiment and find that your WM-918 gauge is not reading correctly, it's not too difficult to properly recalibrate it!
I have to multiply my electronic reading by 1.25 to get a reading which equals the manual gauge, which is my "official" reading.
The electronic gauge is still useful as a guide (saves me getting wet!) and for rainfall intensities.
Location: West Coast Road, Manukau Peninsula, North Island
Unread postby Manukau heads obs »
the increasing the area trick and having software cater for that works well (but it can take a fair bit of fine tuning), and I know of lots of people who have done that around the world
the bigger the rain gauge catchment area, the better....better sampling....i.e official rain gauges are quite large....like the davis VP rain gauge...
note you need to use the area of a circle.....
and not just double the width
James wrote:I have to multiply my electronic reading by 1.25 to get a reading which equals the manual gauge, which is my "official" reading.
The electronic gauge is still useful as a guide (saves me getting wet!) and for rainfall intensities.
Do you have a WM-918? That station's rain gauge can be recalibrated quite easily (once you know how). The instructions can be found here:
So many people used to tell me that the gauge was inaccurate because they "knew" it had rained a lot more than it was displaying. Even I began to believe them after a while, so I went out and bought four different manual gauges. They measured exactly the same amount as our WM-918 gauge. (Actually the electronic gauge was very slightly over-reading due to splash, so I mounted it on a small platform).
I guess when you are sitting inside and the sky opens up and the rain pounds on the roof, most people think, "Gosh, that must be meter of rain right there!", so when they check the gauge and find it was "only" 8mm or so they decide it must be broken.
Location: West Coast Road, Manukau Peninsula, North Island
Unread postby Manukau heads obs »
yup,its people in the towns/cities that often say its been raining lots.....i.e it doesnt take much rain to make the raod wet or the paths wet or for water to run down the side of the road....
