[NLRS] Tropo Maps

[Dr.Gerald Johnson]

>>I don't want to be taken as totally negative, just that I'm sure
>there are more 
>> weather phenomena showing at VHF than at MF to affect
>propagation. 
>
>I think it was Albert Einstein who quipped.  "Every Tom, Dick, and Harry says
>he knows what a Quantum is (a photon), but they are wrong...  Albert E in
>1926
>
>The statement is just as true today as back in 1926.  The closest definition to
>reality that I've been able to locate is one by Gilbert, who wrote:
>
>"A photon is what a photon detector detects..."
>
>Hardly a definition.  But it does explain how hams use them to good effect
>every day.  Until we understand what the heck our buddy Al's Quantum is,
>we won't know all the implications.
>
>...snip...
>
>> I wish that for severe weather forecasting and for understanding
>of odd 
>> none precip radar echoes (like the blobs of summer evenings)
>that there 
>> were thousands more soundings and that they were every few
>minutes. 
>
>I am fairly certain that the NOAA would not be interested in more frequent
>soundings.  I don't know how much it costs to send up a balloon with a
>payload that just gets abandoned, but it has to be $200 or more with the
>Helium involved.  While I have no idea what all they do with the data, I can
>speculate that these soundings become input into their weather models.  

The soundings may be used as input to the weather models, but the models 
tend to discount point events and severe storms. I know for sure that the 
soundings and all their data are used for forecasting severe storms (based on 
my attendance at Severe Weather Conferences at Des Moines over the past 
5 years or so) The area of the curve between the temperature and humidity 
curve is the value CAPE that the higher the CAPE the more likely there will 
severe weather downstream from that sounding.

As
>the Jet Stream moves about, they track the info to model how this induces a
>change in the lower atmosphere.

I've been looking at jetstream forecasts lately. There's a model output product 
that has the highest wind velocity regardless of altitude. Often its disjointed 
and there are only segments of tapered jets with large area having no winds 
over 25 knots. It appears from my plots that the jet sometimes spreads over a 
patch 1000 - 1500 km wide and twice that long, then it reorganizes, but 
sometimes spits. Its never the neat 100 km wide bar show on TV. Looking at 
winds at specific heights (usually pressure heights like 500 mb) the jets are 
sometimes thick, sometimes thin vertically and sometimes the peak wind is 
near the surface.

>
>> There are some UHF vertical sounders that return data
>continuously, but I've 
>> neglected to remember all their operational characteristics.
>
>I would be very interested in any resource of data collected on this topic.  It
>may prove WAY more interesting than the wx info.
>

The sounding data is only available as a graphic as far as I know which is hard 
to convert into numeric data for use in unattended programs.

>> As we've just been discussing on the microwave list, it may well
>be important 
>> to look at IR satellite images for clouds of cold crystals (though
>there's no 
>> elevation information other than temperature and the satellite
>temperature 
>> includes surface through thin clouds or clear skies) and to look at
>storm tops 
>> (as K0SM is doing for predicting rain and snow scatter
>opportunities at 10 
>> GHz) from radar data.
>
>My thinking is the best we can hope for is a general indication of conditions
>that may be present above 40km.  The upper atmosphere is a not nearly as
>variable as the lower atmosphere.  It is simply too thin.  The Jet Stream is an
>indication, but will likely not be the entire picture.  It is hoped that the lower
>atmosphere can be some day viewed with an understanding of what is
>going on above the mesosphere.  
>
>> It appears to me that most of the accepted phenomena at MF
>come from 
>> solar (e.g. UV) ionization of layers too high above the ground for
>balloon 
>> observations. I can't discount there being pressure variations on
>those 
>> heights and ionization intensities. Most often VHF and up requires
>a great 
>> deal greater intensity of ionization that is very uncommon so
>other factors are 
>> predominant.
>
>At MF, I am told that even in the depths of the solar doldrums, MUF does 
NOT
>play a role on MF since the ionization levels are more than adequate to
>support MF propagation.  Only rarely do the MUF's approach 2mHz.  
>
>...snip...
>
>> To me, it sounds like path skewing, spotlighting, path nulls,
>terminator effects, 
>> and reverberations are characteristics of ducts created by solar
>ionization or 
>> varying air densities or humidities. 
>
>Some sort of ducting is the traditional explanation.  But difficult to visualize or
>predict as it sometimes works and sometimes doesn't work--and it seems to
>work in peculiar ways.  Understanding the data inputs needed for prediction
>could prove to be very useful.
>
>...snip...
>
>> Don't discount the possibilities that a duct might be from
>ionization some 
>> places, from temperature gradients in other places and from
>humidity 
>> gradients in other places and a random collection of all three
>(and probably 
>> a couple I've not mentioned) are required to make a particular
>path.
>
>The notion of ducting is greatly debated on MF.  Everyone believes that it
>does happen.  But the mechanisms involved with why it happens today
>and not next Friday is a bit of a mystery.  On MF, the D layer plays a
>significant role.  The refractions actually occur on the E layer, but the D layer
>gets in the way as the gyro frequency of the molecules of air is about
>1.5mHz.  Top band is only 300kHz away at 1.8mHz.  If the D layer serves to
>block signals from arriving at the E layer, and block signals returning back
>from the E layer, the attenuation is greatly increased in the path of interest.
>However, if you consider how holes in the D layer can form, and these 'holes'
>extend up into the E layer, E to F ducting can occur.  Does weather play a
>role?  Quite possibly.

As I said, I suspect nearly every "duct" is a combination of effects. Any work 
that tries to identify only one phenomena may be doomed to fail. Surely the 
right rate and large enough region of changing density due to solar heating or 
differences in moisture or differences in ionization can lead to refraction and 
the appearance of a duct. I think its likely what makes a duct half way around 
the world at 160m may be only due to coupling of several phenomena with 
overlap at their junctions.

>
>> I've not studied it but it seems like the same ionized particles that
>create 
>> aurora can accumulate in the atmosphere to make charged
>and refractive 
>> layers, most often thin for VHF propagation, but one can't rule
>out MF 
>> propagation either. A lot depends on the ionization intensity and
>weather 
>> balloon soundings won't show that and its unlikely the ionization
>will cause 
>> any weather shift, but its worth looking.
>
>I have pondered the notion of star dust before.  Many weather observers 
feel
>that the solar wind does make it down into the atmosphere.  Some believe
>these particulates are needed to form rain as the particulates begin to
>accumulate water on the surface of a particle to form droplets of rain.  More
>intense solar activity is traced to increases in rainfall.  So maybe these
>particulates play a role too.  Central Canada and the upper Midwest are
>known by the term "black hole" in MF circles.  Aurora can (but not always)
>induce considerable attenuation of MF signals.  While attributed to the close
>proximity to the north magnetic pole, perhaps these are also the areas that
>accumulate star dust in the atmosphere.  How this affects MF propagation is
>speculation.

I published (in a private FNW newsletter) a theory of how sunspots affect earth 
weather several years ago. Remember that the tropical trade winds are east 
to west while the temperate trade winds are west to east. Between them 
there is a region of turbulence. In my theory, the tropical trade winds come 
from the drag on the atmosphere from above from the solar wind. So the 
tropical atmosphere spins at a slower rate than the equator. In the temperate 
zones the solar wind is at an angle and so the earth surface friction makes the 
atmosphere keep up with the earth spin. Then that turbulent zone acts like 
gears between two racks to push the temperate winds to the east. When the 
solar winds increase with sunspot activity the effect on the tropical trade 
winds increase, making them faster and pushing that turbulent zone 
northward. There is a statistical correlation between southern US rain and 
midwest US rain and the sunspot cycle. Some places its positive, some places 
its negative. There is a 1.6 year delay. So after the sunspot peak there's a peak 
in tropical storms (not necessarily hurricanes though the last year might hint at 
that) moving into the southern US. And typical SW US weather (dryer in 
summers) moving into the northern plains. As the tropical storms move north 
(little ones as well as hurricanes and typhoons) they bring more moisture north 
to affect atmospheric humidity effects on refraction ducts.

>
>> Then for unexpected directions at MF, what about polarization
>shifts in 
>> propagation? Many long wire antennas have significant cross
>and angle 
>> polarized lobes well off the main axis from the preferred signal
>polarization 
>> that can confuse the observer of the apparent incoming
>direction.
>> 
>> 73, Jerry, K0CQ
>
>The stations able to report direction at MF are not the peanut whistle variety.
>K9DX has 9 - 130' towers in a huge circle to form a directional phased array.
>Many use a set of 4 - 130' tall 1/4wL verticals set in a square and phase
>them.  There are others using a series of 800' to 1000' long beverage antennas
>to provide some indication as to direction.  Mammoth structures actually.
>W0AIH in WI is one of the stations that experience the skewing effects.  These
>are not localized effects, which would be easily explained with back scatter.
>Whole areas of the country will experience similar results.

Polarization can mess up an array, and while the long wire Beverage is 
considered to work best off the end, for horizontally polarized signals it can 
work better off the sides.

>
>> -- 
>> Entire content copyright Dr. Gerald N. Johnson, electrical
>engineer.
>> Reproduction by permission only.
>
>I shamelessly copied the above references without the permission of
>anybody.  Presumably, the author, by posting his response in this public
>forum, provides permission assumptions?  If not, forgive me...
>
>Ford-N0FP
>ford at cmgate.com

The copyright notice is for those who would publish in print or web page what I 
have written. ARRL is one of those that has without asking permission before I 
adopted that signature. I've not caught them since. I found out one of them 
by buying a book (Eastern VHF Conference proceedings) that had I submitted 
the same text, I would have been compensated by being given a copy. So 
they stole that from me. I prefer to not completely give my work away while I'm 
still working on it. Had I submitted for publication the quality of editing would 
also have been higher.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.