Philip

Here are rainfall readings (Jan 2008 and Feb 2008 so far) for my
bog-standard rain-gauge with the rim 30 cm from the ground and my Davis AWS
rainfall gauge with the rim 150 cm from the ground. The differences are
quite amazing.

Jan 2008
Standard: 107.0 mm
Davis AWS: 78.4 mm

Feb 2008 (1st - 10th)
Standard: 26.2 mm
Davis AWS: 19.2 mm

The largest differences occur when windy weather accompanies the rainfall.
The Davis tipping-bucket collector is also in a slightly more exposed
position. I have noted (but don't have the records to hand) that during
rainfall events with little or no wind the difference is negligible.

Because of the exposure differences I am going to move the tipping bucket
gauge sometime soon to a site next to the standard gauge and at the same
height.
_______________
Nick G
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk