MadSci Network: Environment & Ecology

Re: Is barometer more stable in Arizona? or the desert area.

Date: Fri Feb 2 13:15:02 2001
Posted By: David Leonard, Flight Surgeon
Area of science: Environment & Ecology
ID: 979359032.En

Yes, the barometer does change less in the Southwest that it does in the 
Northeast.  You would expect this because of the known higher amount of 
sunshine days.  I found the following passage on the Arizona Visitors 
Information web page:

"With an annual average of 222 clear days, plus 35 partly cloudy ones, 
visitors can make plans that include outdoor activities with confidence. 
Our low relative humidity causes us to boast on the hottest days that
it's a "dry heat." Even days with temperatures over 100 degrees feel 
relatively comfortable due to the low humidity and the cooling breezes."

One of the pilots in my Squadron lived in Yuma AZ for 3 years.  He tells 
me that they would sometimes go days at a time and not have to change the 
altimeter settings in their aircraft.  If you would like to get the 
specific values all the way back into the 19th century, you can purchase 
them fairly cheaply at the web site of the 
National Climatic Data Center   

I find it interesting that your pain is worse with changes in barometric 
pressure.  In my clinical practice patients very frequently tell me that 
the pain in certain joints is worse when the weather is rainy or cold.  I 
have often wondered about the cause of this apparent phenomenon.  I have 
never heard a medical explanation.

Perhaps, as you suggest, pressure changes cause these pains.   However, 
the body is mostly water and some solids all of which are incompressible.  
This allows a deep sea diver to descend to where the pressure is 15 times 
what is at the surface without being compressed to 1/15th his normal 
size.  Barometric pressure  variations are on the order of 50 millibars or 
less.  This is less than 1/20th of the atmospheric pressure or about 1.5 
feet of water or an altitude of a few hundred feet.  The pressure change 
experienced spending the night on the 10th floor of a hotel is greater 
than most barometric pressure changes due to weather.  

Temperature or humidity changes may cause your discomfort, but inside the 
body (except in the fingers and toes) the temperature remains very 
constant.  Humidity is more or less meaningless where there is no air, 
everything is soaking in water.

It could be that we just tend to spend more time sitting in chairs when 
the weather gets crummy.  This extra sitting might make our joints ache.  
Regardless, if staying away from cold fronts and pressure changes makes 
your condition better, the Southwest is the place to go. 

Thanks for your question.

Dave Leonard, MD
Navy Flight Surgeon

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