Firstly; this last month has been unusually harsh by UK standards; as far as my own memory goes, this is one of the most sustained cold snaps I've ever seen. As far as the UK goes, we usually have a week or two of wintry weather and then maybe another couple of incidents later in the year.
There are parts of the UK that don't normally get too much snow that have been under snow for much of the last month.
It's certainly worse than February 2009 (if not for London); it's worse than the 8th-10th of December 1990, and the chill has gone on longer than the heavy snow in February 1981 (when I had the privilege to go tobogganing in a motorbike and sidecar).
Also, weather =/= climate. The overall atmospheric system is a mix of various gases in which there are a continuum of different energies; the sum total of the molecules' energy equating the energy of the system (you'd have to hope!)
If you shove more energy into the atmospheric system, the overall energy distribution of the molecules varies according to the Maxwell-Boltzmann distribution - if you look at the probability density function, the black line represents a low-energy state; the red a medium-energy state and the blue high-energy.
The area under the graph represents the total probability of a gas molecule having an energy in the range covered. So if you look at the black line and pick the energy value '4' (the x-axis), you can see that pretty much all of the black line lies inside that; the probability of a gas molecule having energy < 4 is ~ 1. For the red line, the probability would be closer to 0.5, and for the blue line it's closer to 0.25.
Simply put, shove more energy into a gas and you're less likely to find low-energy molecules; the distribution curve changes such that the energy is more evenly distributed among higher-energy molecules (which makes sense, since gas molecules distribute energy by crashing into each other!).
So far, so academic; this is one of the gems of Victorian physics.
However, an increase in extreme or unusually high-energy weather events correlates with an increase in the overall energy of the system; something like a hurricane is more likely to emerge in a system with a certain proportion of gas molecules over a threshold energy level (known in chemistry as the 'activation energy' for a reaction).
Pick a threshold energy value of 6 on the graph above; the area of the black line >6 is effectively nil; almost no probability of molecules possessing the activation energy to trigger an event.
In the medium-energy state, there are a certain fraction of molecules above the activation energy; a minority, certainly, but the probability of any given molecule having energy >6 is roughly 0.05.
In the high-energy state, the majority of molecules have an energy greater than the activation energy; the probability of a random molecule having >6 energy is roughly 0.6 - i.e. better than even odds.
So while inspection of any single molecule can't tell you much about the system as a whole, the area of the graph beyond the activation energy is very significant; and a comparatively small shift in energy distribution can result in the probability of actual events doubling.
no subject
Firstly; this last month has been unusually harsh by UK standards; as far as my own memory goes, this is one of the most sustained cold snaps I've ever seen. As far as the UK goes, we usually have a week or two of wintry weather and then maybe another couple of incidents later in the year.
There are parts of the UK that don't normally get too much snow that have been under snow for much of the last month.
It's certainly worse than February 2009 (if not for London); it's worse than the 8th-10th of December 1990, and the chill has gone on longer than the heavy snow in February 1981 (when I had the privilege to go tobogganing in a motorbike and sidecar).
Also, weather =/= climate. The overall atmospheric system is a mix of various gases in which there are a continuum of different energies; the sum total of the molecules' energy equating the energy of the system (you'd have to hope!)
If you shove more energy into the atmospheric system, the overall energy distribution of the molecules varies according to the Maxwell-Boltzmann distribution - if you look at the probability density function, the black line represents a low-energy state; the red a medium-energy state and the blue high-energy.
The area under the graph represents the total probability of a gas molecule having an energy in the range covered. So if you look at the black line and pick the energy value '4' (the x-axis), you can see that pretty much all of the black line lies inside that; the probability of a gas molecule having energy < 4 is ~ 1. For the red line, the probability would be closer to 0.5, and for the blue line it's closer to 0.25.
Simply put, shove more energy into a gas and you're less likely to find low-energy molecules; the distribution curve changes such that the energy is more evenly distributed among higher-energy molecules (which makes sense, since gas molecules distribute energy by crashing into each other!).
So far, so academic; this is one of the gems of Victorian physics.
However, an increase in extreme or unusually high-energy weather events correlates with an increase in the overall energy of the system; something like a hurricane is more likely to emerge in a system with a certain proportion of gas molecules over a threshold energy level (known in chemistry as the 'activation energy' for a reaction).
Pick a threshold energy value of 6 on the graph above; the area of the black line >6 is effectively nil; almost no probability of molecules possessing the activation energy to trigger an event.
In the medium-energy state, there are a certain fraction of molecules above the activation energy; a minority, certainly, but the probability of any given molecule having energy >6 is roughly 0.05.
In the high-energy state, the majority of molecules have an energy greater than the activation energy; the probability of a random molecule having >6 energy is roughly 0.6 - i.e. better than even odds.
So while inspection of any single molecule can't tell you much about the system as a whole, the area of the graph beyond the activation energy is very significant; and a comparatively small shift in energy distribution can result in the probability of actual events doubling.