Barbara Murray, age 12, of Milwaukee, Wisconsin, for her question:

How is snow measured?

Suppose the weatherman reports that one inch of snow fell during the night. This means that if there were no bare spots and no deep drifts, the carpet of snow on the ground would be one inch deep. It is possible to measure inches of snowfall by taking many samples and finding an average figure. However, meteorologists are more interested in precipitation measurements, which tell how much moisture actually fell from the clouds.

This is done by translating a snowfall into liquid rain. Samples can be melted and measured in a rain gauge, though this is not practical over a large area. Besides, the quality of the snow varies. One inch of rainfall may equal six inches of soggy snow or thirty inches of very dry snow. To cope with this problem over a large area, meteorologists use an average measurement. They assume that ten inches of snow equals one inch of rain, or liquid precipitation.