[wxqc] Pressure Frequency Analysis

[Steve Dimse]

On Dec 6, 2007, at 8:56 AM, Mark Wyman wrote:

> Having a little background in this myself, just about everything but  
> weather
> systems is "buried in the noise". What I mean by that is there is so  
> much
> going on in the normal atmosphere that it is quite difficult to  
> extract
> anything with real meaning.

This is exactly what Fourier analysis is for. It detects the frequency  
components of what appears to be an irregular wave, in other words  
finding things buried in the noise!

> Your 12 and 24 hour peaks are likely due to
> heating of the sensor during the day causing some error. You need a  
> very
> good sensor set to compensate for this.

No, the diurnal variation in atmospheric pressure is well documented,  
it truly is a tidal phenomenon. It is not even buried in the noise, it  
is clearly discernible in any plot of pressure in areas with  
significant insolation:

http://www.findu.com/cgi-bin/wxpage.cgi?call=CW0925&last=480

The barometric variation due to weather is obviously of greater  
magnitude, but the effect is clear to the eye even without Fourier  
analysis. The effect is greater in tropical regions than the poles,  
and in higher latitudes greater in summer than winter, because these  
areas receive more solar heating.

Steve K4HG