The Metric System and Meteorology

A decade – a period of 10 years that eventually leads to a century. Here’s the weird thing about a decade, and time in general: the older you get, the faster it goes. I know, it seems impossible, but it’s true. I’m sure somebody, somewhere has done a study about it, but that’s another topic for another time (no pun intended).

Decades of the past 100 years have even been given names. The roaring 20s, the turbulent 30s, the fabulous 50s, the swinging 60s and the disco 70s. We also remember decades for significant events within them such as prohibition, the Great Depression, mankind’s first step on the moon, or 9/11. It’s sobering to think about how many monumental events, both good and bad, can happen within a 10-year window.

I was 10 years old in the 70s and still recall a few major events in my life happening in that decade. My first visit to the Astrodome in 1972 (which was, to that point, the best day of my life) and, totally unrelated, when I was forced to learn the metric system.

I remember it vividly. My teacher, Sister Bridget, said the United States was implementing a new form of measuring length, volume, speed, capacity, weight and mass. It was more than a little confusing to me and as it turns out, to most of America.

Congress passed the Metric Conversion Act of 1975 in order to have the United States on the same measurement standard as almost every other country in the world. The act, however, was only voluntary and most of the country ignored the attempt to convert. The metric board was abolished in 1982, but in 1988 new legislation was introduced that designated the metric system as the “preferred system of weights and measures for United States trade and commerce.”

As many of you may remember, the metric system is a decimal-based system of measurement units. These units are for a given quantity, such as length or mass, and relate by factors of 10. Calculations involve the straightforward process of moving the decimal point to the right or left.

You might be wondering how this relates to meteorology. Federal agencies are required to use the metric system, with certain exceptions. The National Weather Service (NOAA) sends all its data and measurements in the metric format. On a weather map, pressure is measured by “millibars,” but for broadcast purposes we use “inches” of mercury. Temperature is measured in “Celsius,” but we use “Fahrenheit” on the air. The reason is simple: the American public, for the most part, understands the U.S. standard better.

Another more complicated meteorological process involving the metric system is the way we measure layers of the atmosphere’s “thickness.” Thickness is a description of how warm a layer of the atmosphere is, usually a layer in the lowest 5 km of the troposphere, or lowest 5,000 yards (approximately). High values of thickness mean warm air, and low values mean cold air. Thickness is measured in decameters, which is a unit of length equal to 10 meters or 32.81 feet. This is a significant measurement because meteorologists determine the rain/snow/ice line by looking at these data.

I still use inches and feet when working around the house and such, but for forecasting, it’s the decimal system all the way. So, to Sister Bridget, thank you for teaching me the metric system – and to Saline County Lifestyles, congratulations on a successful decade of caring and sharing. ν