Jevons effect
From Glossary of Meteorology
Jevons effect
The effect of the presence of the rain gauge on the rainfall measurement.
In 1861, W. S. Jevons pointed out that the rain gauge causes a disturbance in airflow past it, which carries past the gauge part of the rain that would normally be captured. The effect is a function of the wind speed and the height of the gauge from the ground. Rain-gauge shields have been devised to minimize this loss.
