Weather!babble and a history lesson!
Jul. 6th, 2007 10:14 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
eponymous_roseWell, I predicted our little rainstorm today to within twenty minutes of its beginning, using only radar imagery. Huzzah!
That's the fun thing about weather forecasting - if you concentrate on a small enough area and if you know its general weather patterns well enough, you can, with a little practice, predict the next day's weather in an hour-by-hour format, and be just about always right. And then you can extrapolate, using intuition and experience and whatnot. I once sketched up a little weather map of the province based entirely on the clouds I saw on the bus ride to my parents' house - I managed to include all of the large-scale features, in approximately the right place.
And this was the basis of meteorology in the nineteenth century (and, to be perfectly honest, through much of the twentieth, until technology caught up with the calculations) - you look at a certain pattern of winds and pressures, realize you've seen it before, pull out the old records and see what happened last time you saw it. And it's terribly inaccurate, to go about forecasting that way - for one thing, looking at a snapshot doesn't let you know, necessarily, what's going to happen next: is the guy in the picture putting on his jacket or taking it off?
Ah, but then there was good ol' Lewis Fry Richardson, who revolutionized weather forecasting by bringing in the use of numerical weather prediction, using complex mathematical models based on physical theory to extrapolate what's going to happen next. Basically, he was serving in the ambulance unit in Northern France during the First World War, found himself with some spare time on his hands, and decided to create a numerical weather forecast for the 20th of May, 1910. Instead of adopting the common practice of extrapolating forward, he used complex differential equations to extrapolate backward to that particular day. (That's how we test numerical weather models now - feed them the data for July 30th, 1987 and see if they come up with a devastating F4 tornado the next day.)
Alas, his results were way, way off.
(Of course, as it turns out, if he'd had a smoothing algorithm to work out the kinks that come from using higher-order polynomials, he would've been nearly bang-on. But everyone likes to complain about how the weather forecasters get it wrong, and it's nice to have a historical basis for that.)
Anyway. Um. Numerical modelling's a tricky business - it averages when it shouldn't necessarily do so, marks some data as spurious and to be ignored when it's really just plain weird.
And then chaos theory comes in and blows the whole thing to hell.
It's awesome. I can't wait for classes to start up again. :D
What else is new?
Well, speaking of numbers, if you sum together the years I've spent fencing and the years I've spent playing piano, you get my age. Uh. Yeah. Not really that exciting, but it'll only happen once.
Heat wave's broken! My room's 29.7 degrees C and falling. It smells like rain.
That's the fun thing about weather forecasting - if you concentrate on a small enough area and if you know its general weather patterns well enough, you can, with a little practice, predict the next day's weather in an hour-by-hour format, and be just about always right. And then you can extrapolate, using intuition and experience and whatnot. I once sketched up a little weather map of the province based entirely on the clouds I saw on the bus ride to my parents' house - I managed to include all of the large-scale features, in approximately the right place.
And this was the basis of meteorology in the nineteenth century (and, to be perfectly honest, through much of the twentieth, until technology caught up with the calculations) - you look at a certain pattern of winds and pressures, realize you've seen it before, pull out the old records and see what happened last time you saw it. And it's terribly inaccurate, to go about forecasting that way - for one thing, looking at a snapshot doesn't let you know, necessarily, what's going to happen next: is the guy in the picture putting on his jacket or taking it off?
Ah, but then there was good ol' Lewis Fry Richardson, who revolutionized weather forecasting by bringing in the use of numerical weather prediction, using complex mathematical models based on physical theory to extrapolate what's going to happen next. Basically, he was serving in the ambulance unit in Northern France during the First World War, found himself with some spare time on his hands, and decided to create a numerical weather forecast for the 20th of May, 1910. Instead of adopting the common practice of extrapolating forward, he used complex differential equations to extrapolate backward to that particular day. (That's how we test numerical weather models now - feed them the data for July 30th, 1987 and see if they come up with a devastating F4 tornado the next day.)
Alas, his results were way, way off.
(Of course, as it turns out, if he'd had a smoothing algorithm to work out the kinks that come from using higher-order polynomials, he would've been nearly bang-on. But everyone likes to complain about how the weather forecasters get it wrong, and it's nice to have a historical basis for that.)
Anyway. Um. Numerical modelling's a tricky business - it averages when it shouldn't necessarily do so, marks some data as spurious and to be ignored when it's really just plain weird.
And then chaos theory comes in and blows the whole thing to hell.
It's awesome. I can't wait for classes to start up again. :D
What else is new?
Well, speaking of numbers, if you sum together the years I've spent fencing and the years I've spent playing piano, you get my age. Uh. Yeah. Not really that exciting, but it'll only happen once.
Heat wave's broken! My room's 29.7 degrees C and falling. It smells like rain.
