Thursday, October 14, 2010

The Meteorology of the Chilean Mine Rescue

Now that all of the miners are safe, it is interesting to think about some of the meteorological aspects of the disaster--and of the misinformation provided by the media.

Some of the media suggested that the miners could get the bends from "rapid decompression", but this is nonsense!

The level of the mine entrance, where the drilling is taking place, is at roughly 2400 ft above sea level, and the miners were trapped at a level a few hundred ft above sea level. Clearly, the pressure was higher where the miners were--roughly 8 % higher. And it took them about 15 minutes to make the change as they were lifted out. This is nothing to worry about! Virtually all of you experience this change many times each year. An example: drive to Snoqualmie Pass (elevation roughly 3200 ft) from the west. The last fifteen minutes you gain roughly the same elevation in the same amount of time! Or when you take off in a plane, take a long lift ride while skiing, take that gondola ascent on vacation, etc., you experience the same or worse!

Then there was the "steam" coming out of the hole (click on picture to see video):

Why the cloud coming out of the hole? The temperature down in the mine was very warm (90-105 from various reports) and there were sources of moisture down there. The air had sufficient water content that when it hit the cool nighttime air, it was cooled to saturation--thus the fog. It looked to me that temperatures were fairly cold during the evening rescues---40s F perhaps from the jackets people were wearing. A small contribution could also have come from the expansion cooling of the air as it rose.

The region surrounding the mine is very, very dry--in fact one of the driest places on earth...the Atacama Desert (see map). Some locations have never observed rain, and in others they receive perhaps a few hundredths of an inch per year. Why so dry? Sinking air from a subtropical high, the high Andes preventing moisture form moving from the east,

Mars or the Atacama?
and the coastal mountains preventing moisture movement from the west. Plus an inversion aloft that stops the air from moving over the coastal mountains.

And talking of media issues...which country is wrong in this map?

The mine site from space

LOCAL WEATHER ALERT: Looks like dry conditions for the next 4-5 days with considerable sunshine!


Jim S said...

Great post Cliff. I even commented while watching the news that the idea of getting the miners getting the bends was pure poppycock!

natchrl8r said...

Speaking of misiniformation, the map you copied is showing Brazil where Argentina should be!

SteveM said...

On the subject of Chilean meteorology, Santiago weather is also interesting. The Santiago airport is in one of the foggiest regions of the country, with 70 days of fog per year! Something about marine air working its way up the valley and becoming trapped under the inversion common to the basin in which Santiago is located. Frequent visitors to Santiago will have experienced the joy of landing in Mendoza, Argentina (not Brazil as on the map)and waiting parked on the tarmac with a dozen 747s at a tiny airport there for the fog at the Santiago airport to "burn off." Once it does, the short hop from Mendoza to Santiago over the Andes is spectacular!

lamont said...

historically, miners have gotten the bends, but in pressurized mines where the pressure is being used to keep water out of the mine.

with this unpressurized mine the miners were doing the equivalent of about a 2.5 foot deep saturation dive -- not enough to cause the bends. that isn't even enough to cause any bubbling in the tissues at all, you'd need to have a mine 4x as deep as that to cause any tissue oversaturation of nitrogen. you'd need something like 10x the depth before getting bent was a problem.

John Franklin said...

A comment and question on your contrail post. Like you I find contrails aesthetically pleasing but now also think of their downside. I know that high altitude airplane emissions cause pollution (through emitting nitrogen oxides and sulfur oxides)that are estimated to cause about 8,000 deaths per year globally. But what about the role contrails play in climate change by increasing cloud cover and their high altitude emissions of CO2. Thanks.

mjgrota said...

Hey we never heard what happened to the miner who had a wife and mistress waiting for him? No doubt he wanted to be the last one out. Maybe he stayed?
I guess the Columbus graphics artist was in coloring class instead of geography class. Question what state is due north of Columbus Ohio?

citabria90 said...

Talking about media "issues," (flat-out ignorance and stupidity, IMHO), I'm a private pilot, and every time there's some kind of aviation incident, the TV media (especially the locals) have a field day with misinformation. They're always quick to point out that the pilot "DIDN'T FILE A FLIGHT PLAN! OMG!", notwithstanding that under VFR (visual flight rules) flight plans are not required. The best example of media stupidity was a fairly recent (12-24 months or so, I think) non-fatal crash of a FedX aircraft. A local TV station reported that a FedX "jet" had crashed, yet in the accompanying photo, it was clearly a prop aircraft (Dash 8). Arrrrgh!

Peter said...

Wow I never knew that weather paid a roll in mining! Is this always true?
P.S. The mine site really did look like mars!

Cheryl said...

Wow, I sure hope a news outlet didn't actually USE that map in their broadcast re: the miners! Oh wait, of COURSE they did. Can you say muy estupido?

Seabear70 said...

As a professional saturation diver, I'd say the only possible diving type injury would be a pneumothorax.

This would of course require them to hold their breath from the bottom of the shaft to the top. Even then, I won't guarantee it, not only because 15 mins is a long time to hold your breath, but because I don't know of anyone who has managed that in that little pressure difference.

Technically it is possible though.