Topic: calibrating rain gauge

[offroadjosh]

so i found out my davis gauge reads low  about .05inches  (checked with cocorhas gauge at same height in same location) so if im correct thats 5% off or about one turn of the screw???

[mackbig]

What length of period did you analyze, what was the rain rate during the period, and how many periods did you base your results on???

Since the stated accuracy is +-4% to +-5% based on the event, I would not start messing with calibration.

Andrew

[d_l]

I've been surprised that everyone seems to think their Davis rain gauges need to be calibrated.  I've always assumed that a NIST-standardized calibrated setting was part of the manufacturing process at the factory (this isn't the same as an individual unit NIST calibration check).

So I thought I would drag out my old pre-CoCoRaHS inner tube and cone to verify the Davis gauge's results and take advantage of the abnormally high number of rainy days we are having.  Normally you can't do this in the desert and all you end up collecting in the calibrated tube is bird poop and bugs.  My pre-CoCoRaHS's outer tube is so sun crazed that I'm almost afraid to touch it for fear that it will crumble or that the bottom will fall out of it at any moment. 

So far based on a few rain events, both hard and gentle, I've found that the Davis gauge is either dead equal to or one tip (0.01") less than the 4" gauge. The 4" gauge is in a more wind-sheltered location and is at a lower height than the Davis ISS so this also assures me that the rainfalls with low to modest winds (0-8 mph) are being properly measured.

[offroadjosh]

Thanks, maybe i will leave me davis gauge alone then.


Josh

[Wx4U]

Josh, I don't think I would touch the calibration on the rain gauge. I have had a Davis located about 10 ft. from a 4 in. gauge since April. The total rainfall has been about 8 in. with only .05 in. difference. Remember, it only takes a couple of drops to tip or not tip the bucket.
Bob