Friday, January 25, 2013
Well, after one of the most horrendously academic stretches ever, I’m back to having some free time. Most people would consider this break in work I am experiencing relatively small compared to their schedules, but I consider it massive in depth, breadth, and lack of activity. (Although I have to admit, now I’m finishing this post on February 3, and the work is upon me once more.)
Most people would also consider the title of this post to be one of the dumbest headlines they’ve ever read. But once again, I consider it differently.
Over the past week, I’m sure many of you became familiar with inversions. When a parcel of air is forced to rise, it expands and cools due adiabatic processes. For those of you who don’t know, an adiabatic process is a process where there is no heat exchanged with the environment. When an air parcel rises, the amount of heat in it stays the same, but it expands due to it being surrounded by lower environmental barometric pressures as it increases with elevation. When it expands, it must hold the same amount of heat energy, but does so over a wider area. The result is a lower density of kinetic energy per unit volume, because the kinetic energy is constant but the volume increases. I don’t know the best way to explain all this stuff because I haven’t taken any classes on adiabatic processes apart from a lecture on it in my Atmos 101 class with Cliff Mass 2011 fall quarter, but that’s the general idea. When air rises, it cools and expands; when air sinks, it warms and compresses.
This is why we see temperature generally decreasing with height. But alas, things are not always so simple.
The thing about cold air is that it is dense. The coldest locales in the U.S. are not the highest mountains (sorry Coors Light, there are places much colder than the Rockies). One example that comes to mind is Peter Sinks, a natural, high elevation sinkhole in Northern Utah. Peter Sinks is shaped like a bowl, and at night, the coldest air in the region flows right into Peter Sinks, as the bowl shape is conducive to accumulating this dense air. The air that is relatively warmer stays on top of the bowl. In this scenario: the air is colder at the bottom than at the top, and because cold air cools even further when it rises and the warmer air above warms when it sinks, the atmosphere is extremely stable because air parcels do not want to move. This is an inversion… the “reciprocal” of the typical atmospheric configuration we see on Earth.
There have been some incredibly strong inversions over the past week. From January 17 to 22, there were a total of 6.5 hours of visibilities over a half mile. This means that over this 5-day period, it was foggy ~95% of the time. Credit to Scott Sistek for calculating this gloomy statistic. Yet while it was cold, smoggy, and disgusting down here, the snow levels were sky high in the mountains… above 12,000 feet. In fact, Paradise got into the 60s while we were in the 30s. Pretty ridiculous.
Anyway, I’ve got to go to bed… I started this post in January and finished it off by writing the last two paragraphs at 1:45 A.M. on Super Bowl Sunday. I’ll try and keep you posted more regularly on what is going on. And I will have a post on WeatherOn this afternoon.