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Air Masses: A Taste of Weather

© Keith C. Heidorn

Long before meteorologists began drawing fronts and cells of high and low pressure on national/international maps, those attuned to the skies understood that different masses of air had different, distinguishing properties.

For example, around 400 BC, Hippocrates wrote in On Airs, Waters, and Places that health could be tied to the source of the winds flowing into the city. While his linkages between weather and health do not all hold today, this work showed an understanding of the differences between the properties of air flowing from different regions.

Until the 17th Century, early weather observers and folk forecasters used their senses to distinguish differences between air masses. Humans likely first recognized differences between air masses in prehistoric times when they sensed that changes in weather conditions had recognizable, repeatable patterns and common sensual properties: hot or cold, damp or dry.

When I wrote a poem called "A Fine Vintage" several years ago, I took the concept of air mass analysis and used the metaphor of wine tasting to describe different types of airs. In it, I described how our senses of smell and sight, and at times taste, can distinguish the type, origin and travels of the air surrounding me at any given moment.

As instruments to measure atmospheric properties, such as pressure, temperature and humidity, became widespread, weather observers could now describe the differences between air masses numerically. Once networks of simultaneous weather observations became established in the 19th Century, air masses were revealed to be very large volumes of air with similar temperature and moisture characteristics. Formal characterization of air masses (known as air mass analysis) emerged about a century ago from the famed Bergen School of Norwegian meteorologists, who also developed the frontal theory we now take for granted.

If you were to look into older geography or science books (pre-1930 in the US), you would find weather maps without the usual warm and cold frontal systems drawn on them. Instead, you might find a code of two or three letters such as: cPk or mT, or words such as "cold, dry" or "hot, humid" written near the centres of high pressure.

Weather forecasters now rely on a variety of measurements, such as temperature and humidity, to tell them of the "taste" and "bouquet" and "colour" of the various air masses. Good weather forecasts can be built on a solid knowledge of the properties of the various air masses upwind of their forecast zone, even when the air mass of concern is hundreds or thousands of kilometres away.

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