1904: Meteorology Becomes A Science

by Michael Tobis     Department: Earth

For a very long time, there have been two informed schools of thought about meteorology.

The first group believes that the principles of meteorology are necessarily the principles of physics and chemistry, and thus meteorological problems (such as weather prediction and climate dynamics) can only be addressed by applying the methods of physics.

The second group believes that while physical principles must hold, the way in which they hold is much too complicated to be practical, and that the best one can do on many kinds of problems is to determine a heuristic from observations. While each group occasionally makes a grudging concession to the other, the whole question of limitation vs possibility is an ongoing theme.

When we actually start to look at the emergence of climate prediction and scientific concern about human impacts on climate, we will see both of these threads influencing professional attitudes, while the general public is unaware of this philosophical split.

An early example of this theme came up in the previous installment of this series.

In the 1840s, an American, James Pollard Espy, applied new physical understanding in the thermodynamics of water phase changes to understand the nature of a convective cloud, thinking to build a theory of meteorology around that understanding. Meanwhile, with the emergence of the widespread observations, and in a northern European environment where isolated convective cloud formations were much more rare, opinion coalesced around a set of ideas based on an as-yet unexplained but observationally clear rotation of large-scale patterns in the atmosphere. We also saw that so much contention appeared between these camps that they were unable to realize that both points of view were mostly right and slightly wrong. Understanding the atmosphere did not progress much in the nineteenth century, though empirical skill in forecasting did advance.

Weather prediction already existed as a profession before meteorology as a fertile scientific discipline arrived on the scene. In 1900, while physics was on the brink of breaking out of a highly developed classical theory, meteorology as science did not exist, although it is widely suspected among the scientists of the day that it ought to be possible.

The person who did the most to create the transition was the Norwegian, Vilhelm Bjerknes. Alas for those of us scientists from less educated families, professorship runs in families. Bjerknes' father was a professor of mathematical fluid dynamics, and the younger Vilhelm Bjerknes followed in his footsteps, obtaining some theorems about stratified fluids where different layers move independently. It was his search for real world applications of these results that first led Bjerknes to become interested in meteorology around 1900.



Vilhelm Bjerknes  was of the school of thought that believed that meteorological phenomena could be derived from first principles. By1904 he was proposing to develop methods of weather prediction based on the known principles of physics. His arguments were sufficiently persuasive that he received a lifelong stipend from the Carnegie Foundation (lasting form 1905 to 1941) to pursue this.

(I would be happy to entertain inquiries from the Carnegie Corporation at their convenience.)

Bjerknes formulated a system of equations describing the motion of the atmosphere. Unlike electromagnetics, the system being described is messy, and there is little likelihood of a perfect mathematical representation, but Bjerknes' version is still the most commonly used approximation. Model builders call his system "the primitive equations" for reasons which escape me. (Actual model equations are derived from these in various ways.) Bjerknes was as close as meteorology ever got to having its own James Clerk Maxwell.

That system, still at the core of our work, is an extension of the basic equations of fluid dynamics (called the Navier-Stokes equations) in a rotating environment, combined with the thermodynamics and kinematics of water. It's not a perfect model but it is still the best compromise between tractable mathematics and an effective description of the real world for many purposes.

Bjerknes' mathematical formulation did prove to be a basis for understanding the large mysterious swirls of storms that are so prominent in our satellite "loops" (movies) that we see on weather reports. I am old enough that when I watched weather predictions on TV nobody had ever seen these, though some people understood matters well enough to imagine them.

Bjerknes work created a mathematical discipline of atmospheric science which remains vibrant and interesting today. It feeds into oceanography, planetary science, and astrophysics. It has a peculiar and beauty that I won't endeavor to describe here, but if you care to direct your attentions in that direction and you are mathematically adept, you too can quite thoroughly understand the nature of those gigantic swirls that bring fronts and storms and rain and calm to you every day.

Nevertheless, although Bjerknes and his students began the process of making a classical science out of what had been a hodgepodge of observations and heuristics, he never succeeded in his goal of scientific weather prediction. During the first world war he was impressed into service by the Norwegian government as a weather forecaster, and he was forced to use the seat-of-the-pants heuristics of the skeptics of his day, those who believed that there was something about the weather that made it impossible to apply calculations to it.

The story of the man who made the first attempt at an actual mathematical weather prediction is one of the most fascinating tales in the history of science. We'll take it up next time.

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In this series, I've been tracing the emergence of climatology as a science by looking at its roots in the origins of meteorology. This is the fourth article in the series. I'll get to the controversies about climate eventually. This is an effort to create some shared context in which to think about them.

Here are the first installments:

Like a model on the cover of a magazine: Science is about models

The Elephant's Trunk: Origins of Meteorology

The Storm King: The Man Who First Understood Rain Clouds

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