[NLRS] Tropo Maps

[Ford Peterson]

From: "Dr. Gerald Johnson"
Sent: Wednesday, January 12, 2005 12:06 PM
Subject: Re: [NLRS] Tropo Maps


> As far as I can remember, MF propagation hasn't been linked to weather 
> conditions just to solar induced ionizations. I'm sure AM broadcast research 
> goes back to 1922. For sure thunderstorms adversely affect received signal 
> to noise ratios though.
>
> At VHF and up many weather conditions are known to affect propagation 
> and some modes like Sporadic E and Aurora E haven't been explained yet. 
> There seems to sometimes be correlation between storm tops and Sporadic 
> E cloud initiators but sometimes not. Probably what we observe as Sporadic 
> E events have several different causes, sometimes mutually exclusive, 
> sometimes working together. Wind shear at altitude is a possible source of E 
> clouds.
> 
> I think that weather phenomena below 50,000 feet may be too restrictive, 
> but the balloons don't have any idea about electric charge and charge 
> from solar insolation or other events is what makes propagation reflectors 
> whether at 1.8 or 50+ MHz.
> 
> Give it a shot, huge hard drives aren't very expensive these days, look at all 
> the available sounding data, I think you will find that the data BELOW 50K 
> feet will be the least interesting for all but temperature inversion events, 
> warm air overruns at fronts, and high pressure domes.
> 
> 73, Jerry, K0CQ

Jerry, and others.

One of the participants in this study is Bob Brown-NM7M.  Bob is 82 years old now, and he suffers from Arthritis, which makes even simple tasks like typing difficult.  But he has been in the business of looking at propagation since the beginning days of radio.  He was instrumental in the design and execution of the high altitude balloon experiments back before dirt was made.  He was instrumental in the mission critical aspects of the initial manned space shots.  John Glenn went into orbit to see if we could talk to him.  That was a significant part of the initial mission.  Bob was on the Aleutian Islands (Alaska) when the huge nuclear tests were being detonated in the Pacific, back when Moby Dick was still a guppy.  Bob held in his hands the information needed to publish the original work on what we now call the VanAllen belts.  Dr. VanAllen beat Bob to the punch by a couple of weeks.  His client list includes notables like the Navy, NASA, NSA, and others.  I am honored to help him try to figure this out today.

Bob tells me that the weather aspects have been studied, and interesting anomoly do happen, but not in a documented way--especially at MF.  The NOAA information is way incomplete as the real weather of interest is at 100km and the wx balloons only go to about 45km.  So some guess work as to what is happening above the top of the data set may be important to understanding what is happening.  The NOAA is more interested in the mesosphere, which is where weather occurs.  But the data is there, somewhat hap-hazardly collected, but there none-the-less.  I am certain that it suits their purposes just fine, which is why they pay people to collect the data.  Adapting the data for this purpose may be a stretch.  But worthy of a closer look-see.

I have already observed interesting issues involving air pressure.  Pressure can fall to a certain point, then increase again before falling to next to nothing.  At the ground, the pressure is about 1000 milibars and drops to 1 or 2 by the time you get to 40km.  So there is not much weather there to begin with.  Wind shear may be important to this as well.  As well as the temperature, dewpoint, and relative humidity.  I know that when I shine a light through an aquarium, you see the refractions very clearly.  What happens to a radio signal in a very thin viscous gas remains speculative.  Different frequencies will likely react differently.  So we are going to look at it more closely.  The focus is on MF but the VHF/UHF aspects may prove interesting as well.

Stay tuned...

Ford-N0FP
ford at cmgate.com