Weather Whys; Nephoscope

This is weather-wise. Even the casual observer can often note the movement of clouds, and a careful eyes-only observation can sometimes give a good idea of the direction of that movement. But for meteorological purposes, more precise measurements are sometimes needed. Satellites can take those measurements on a large scale, but they have limited resolution. So, to measure the movement of a single cumulus cloud, a different instrument is required. The device is relatively simple, but it plays an important role in the ability to pinpoint the direction of cloud movement. That device is called a nephoscope, and there are two types. One is the mirror vision variety, in which a horizontal mirror of dark glass reflects the clouds in the sky. In order to view the clouds, a special eyepiece is attached to the mirror's support, and direction vectors are etched onto the periphery of the mirror, so that cloud movement can be matched with the points of the compass. The other type of nephoscope is the direct viewing model.

It looks a lot like an upended rake, with straight tines extending upward from a horizontal bar mounted on a tall pole. At the bottom of the pole is a circular scale with the points of the compass marked on it. To determine cloud progression, a person must simply rotate the pole so the tines are lined up with the clouds' direction of movement. Comparing that to the scale provides the precise direction of travel. So not all weather devices are complicated. Sometimes even a simple instrument can provide observations which are a great improvement over those made with only human senses. We'd like to know what you think of WeatherWise. Please write us at WeatherWise, KGOU Radio, the University of Oklahoma, Norman, Oklahoma, 73019-0250. WeatherWise is made possible by a grant from the National Science Foundation. For WeatherWise, I'm Drew Barlow.