Alter shield
From Glossary of Meteorology
A type of rain or snow gauge shield consisting of freely hanging, spaced slats, arranged circularly around the gauge, the height of which is the same as the gauge height.
The purpose is to reduce undercatch due to wind by forcing the air toward the surface instead of accelerating over the gauge orifice.
Compare Nipher shield.
Alter, J. C. 1937. Shielded storage precipitation gauges. Mon. Wea. Rev.. 65. 262–265.
