Читать книгу Weather For Dummies - John D. Cox - Страница 20

The atmosphere has a physical characteristic, like a personality trait, that sometimes drives forecasters to distraction, especially as they try to predict what the weather is going to be like beyond a few days.

All disturbances in the atmosphere grow and decay. Some disturbances are big enough to be measured — and “seen” by computer models — and predicted. Other disturbances are too small. In such a chaotic system, very small disturbances can lead to big disturbances over time.

When he discovered this characteristic of weather in the early 1960s, meteorologist Edward Lorenz at the Massachusetts Institute of Technology came up with an interesting way to describe the problem. Imagine a butterfly in the jungles of the Amazon fluttering its wings and setting in motion a subtle whirl of breeze that travels and magnifies through the atmosphere over time. Farther and farther it goes, bigger and bigger it grows. Two weeks later, this breeze results in a tornado over Kansas. This is known as the Butterfly Effect.

Should the Butterfly Effect be taken literally? No. But forecasters ever since then have taken very seriously the big idea behind it. The atmosphere’s way of doing things is on a scale that is always going to be finer, or more exacting, than the scale for the data on initial conditions that goes into the numerical forecast models. This means that, no matter how much computer power is thrown into the job, it is simply not possible to create a 100 percent accurate forecast, or a detailed weather forecast beyond about two weeks.