dsnow/dt

bonuscats.com
Not this stuff, again!
We’re having a teeny bit of snow. Compared to the winter a lot of other people have had, we’ve been getting off easy. But that doesn’t mean I won’t grouse about it.

I’ve been checking up on the blog by Professor Cliff Mass (he teaches meteorology at the U of Washington, and was once a grad student of Carl Sagan). I’ve been following his weekly weather bit on a couple of the local NPR stations for years, where he nerds out about the science of weather. Today’s “nowcast” about our current series of alternating cold and warm fronts.

He was talking about the various computer models that they run, and how as they run them again and again they all change in the same way. He said, “Meteorologists call this dprog/dt or dmodel/dt (those who know some calculus will understand the name!).”

To unpack that joke, in math we are often concerned with rates of change. So we’ll talk about dx/dy, with the “d” referred to delta or change, and the “x” and “y” each being variables representing some quantity you might be monitoring, so “dx/dy” can be transliterated into English as “the change in x in relationship to the change in y.” Which sounds weird and abstract until I point out that every time you look at the speedometer on your car, it’s showing the “the change in distance in relationship to the change in time.” Most of the time we in physics and other physical sciences, the variable “t” represents time, so “dt” is “the change in time.” So Cliff’s comment about “dprog/dt” would be “the change in [the result from the] program in relation to the change in time” and “dmodel/dt” would be “the change in [the result from the computer] model in relation to the change in time.”

Anyway, it made me think of what may be my new favorite rate of change: dsnow/dt, “the change in the amount of snow in relationship to the change in time.”

And let me just say, I hope the slope of that curve goes negative sooner, rather than later. (Which is a nerdy way of saying I want the dang snow to go away!)

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