How Google Researchers Used Neural Networks to Make Weather Forecasts
Freeman writes:
A research team at Google has developed a deep neural network that can make fast, detailed rainfall forecasts.
The researchers say their results are a dramatic improvement over previous techniques in two key ways. One is speed. Google says that leading weather forecasting models today take one to three hours to run, making them useless if you want a weather forecast an hour in the future. By contrast, Google says its system can produce results in less than 10 minutes-including the time to collect data from sensors around the United States.
[...] A second advantage: higher spatial resolution. Google's system breaks the United States down into squares 1km on a side. Google notes that in conventional systems, by contrast, "computational demands limit the spatial resolution to about 5 kilometers."
[...] Google says that its forecasts are more accurate than conventional weather forecasts, at least for time periods under six hours.
[...] Interestingly, Google's model is "physics-free": it isn't based on any a priori knowledge of atmospheric physics. The software doesn't try to simulate atmospheric variables like pressure, temperature, or humidity. Instead, it treats precipitation maps as images and tries to predict the next few images in the series based on previous snapshots.
[...] Specifically, it uses a popular neural network architecture called a U-Net that was first developed for diagnosing medical images.
[...] To produce a weather forecast, the network takes an hour's worth of previous precipitation maps as inputs. Each map is a "channel" in the input image, just as a conventional image has red, blue, and green channels. The network then tries to output a series of precipitation maps reflecting the precipitation over the next hour.
Like any neural network, this one is trained with past real-world examples. Thousands of past real-world weather patterns are fed into the network, and the training software tweaks the network's many parameters to more closely approximate the correct results for each training example. After repeating this process millions of times, the network gets pretty good at approximating future precipitation patterns for data it hasn't seen before.
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