Science's gains from computer modeling hard to dispute

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I have written previously about the use of models and algorithms to study various scientific phenomena. I had my first experience with these methods in my first job for which my education was important.

Just after completing my master of science degree in physics in 1972 I worked at the Naval Electronics Laboratory in San Diego. I was a junior member in a group studying how radar traveled (propagated) through layers in the lower atmosphere.

This was of interest to the Navy because of the French development of the Exocet missile. It had been designed to fly only a few meters above the water and strike warships. Attacking ships could launch their missiles from beyond the horizon and the missiles could not be seen by conventional radar until they were only a few miles away — too late to react.

Was it possible to give ships more time by developing radar that saw beyond the horizon? The senior, lead scientists in the group would take a very sophisticated mathematical approach while I was asked to attempt something simpler. Given the limitations of computing in the early ’70s, a fast simple approach, though not as accurate, might have some utility.

The research was motivated by how it was thought radar propagated through something called an evaporation duct. The term duct was used because it describes something traveling while being confined to a specific space.

Electromagnetic radiation, of which radar is one variety, is refracted (bent) when passing through multiple layers of air, each having a different humidity. Evaporation from the surface of a body of water creates a profile where humidity diminishes at ever greater heights.

The profiles were such that they bent radar downward toward the water. Upon striking the surface, some of the radiation is reflected upward where it is, once again, refracted back to the surface. Travel was largely confined so that the layers were effectively acting like a duct. It was a little like skipping rocks on a pond.

Would this enable radar to follow the Earth’s curvature extending into the space below the horizon?

Meteorologists in the group were tasked with studying the conditions giving rise to humidity profiles and assess how reliably favorable profiles persisted. They had the enviable job of traveling to locations around the world and sending up weather balloons to measure humidity profiles under different conditions.

Wind velocity and air and water temperatures contributed to the strength of evaporation ducts, so understanding prevailing weather patterns around the globe was important.

With a profile in hand, could we model radar propagation through the atmosphere? What was the optimal wavelength? At what height would one place the radar dish to exploit the evaporation duct? Would the intensity of the radiation be sufficient to return a detectable signal upon striking a target?

This was applied research, using what was well known about the propagation of electromagnetic radiation to a specific task. We had equations we could use in our computer programs that were precise in their representations of the refraction phenomena. We knew the kinds of loses in intensity that occurred upon reflection from a flat surface, but what effect would various ocean surface conditions have?

Of course, once the computer modeling was complete, their predictions were tested. I lost track of the project once I left the group, but my understanding was that enthusiasm for it withered. Though the models worked, I think it was shown the evaporation ducts weren’t persistent enough to justify the cost of revamping the Navy’s radar.

Though it had been a great experience for me, my heart was in studying the more fundamental phenomena that physics embraces. So, I returned to graduate school to pursue a doctorate.

I had been given the chance to use my knowledge in a real-world application. My one year had by no means made me an expert in climatology or even in the propagation of electromagnetic waves in the atmosphere. But, it had given me an appreciation of how one builds computer models of such phenomena.

Other researchers have developed very sophisticated models to study how electromagnetic infrared radiation generated from the Earth’s heat is radiated into space. This cools the planet. On the other hand, incoming sunlight warms the planet. Ideally, these two processes balance one another resulting in relatively stable temperatures.

Just as we used what was known about refraction of radar, climate scientists use their knowledge of the effects of greenhouse gases on the propagation of infrared radiation. The basic phenomena are well understood, no serious controversy exists here.

They incorporate these effects into their models. Should that propagation be diminished, the amount of heat dissipated into space would be reduced. And, just as the Navy group tested their models’ predictions, I have no doubt climatological models are tested in every way possible.

No matter how well the basics are understood, incorporating them into climatological models isn’t easy. But, it astounds me that people having no knowledge of these models assert they are flawed.

Scientists from a variety of disciplines contribute to these studies. An overwhelming preponderance of them thinks climate change is primarily driven by greenhouse gases. To think that a worldwide conspiracy exists among these scientists isn’t credible.

I hope offering this example helps in understanding the vital role of modeling in applied research. Though the findings of basic science are always tentative, applied science assumes some findings are so certain they can be used as needed.

To do otherwise would greatly inhibit progress. We would be poorer for it and run the risk of blundering into unforeseen dangers.

Steve Luckstead is a medical physicist in the radiation oncology department at St. Mary Medical Center. He can be reached at steveluckstead@charter.net

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