Posts Tagged ‘Weather forecasting’

Climate model results depend upon which computer they run on!

June 26, 2013

Robust models indeed.

Washington Post:

New Weather Service supercomputer faces chaos

The National Weather Service is currently in the process of transitioning its primary computer model, the Global Forecast System (GFS), from an old supercomputer to a brand new one.  However, before the switch can be approved, the GFS model on the new computer must generate forecasts indistinguishable from the forecasts on the old one.

One expects that ought not to be a problem, and to the best of my 30+ years of personal experience at the NWS, it has not been.  But now, chaos has unexpectedly become a factor and differences have emerged in forecasts produced by the identical computer model but run on different computers.

This experience closely parallels Ed Lorenz’s experiments in the 1960s, which led serendipitously to development of chaos theory (aka “butterfly effect). What Lorenz found – to his complete surprise – was that forecasts run with identically the same (simplistic) weather forecast model diverged from one another as forecast length increased solely due to even minute differences inadvertently introduced into the starting analyses (“initial conditions”). ..

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