[NLRS] Skew - T data for over Lake Superior

Tue, 11 Feb 2003 07:44:47 -0600

Well, if the weatherman was only wrong 80% of the time, thats 10% better
than here !!

Eddie, regarding the PUM beacons, do you know of anyone who may have done
any long time observation and recording of the beacon strengths over water
paths, especially on the high band beacons ?

73, Jon
W0ZQ

                      "Fast Eddie"                                                                                                     
                      <[email protected]       To:       "Baker, Donn B" <[email protected]>                                       
                      >                          <[email protected]>                                                                    
                      Sent by:                   <[email protected]>                                                                
                      nlrs-admin@mailman       cc:                                                                                     
                      .qth.net                 Subject:  Re: [NLRS] Skew - T data for over Lake Superior                               

                      02/10/03 06:24 PM                                                                                                

Yes there is a lot of ducting... Variances in signals on N8PUM's beacons
and
other stations to Thunder Bay have always been noted. I don't have any data
except for what I've heard everyday. When my beacon was running similiar
reports we received from stations in upper Michigan... The cold water
effects weather patterns very much and therefore makes the weatherman wrong
about 80% of the time...

Eddie VE3KRP/VA3KRP EN58ij
----- Original Message -----
From: "Baker, Donn B" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Monday, February 10, 2003 1:00 PM
Subject: RE: [NLRS] Skew - T data for over Lake Superior

> After our trip last fall, I did some looking for data myself.  I did get
> some info from the Houghton, MI area from a retired Michigan Tech
professor
> (W8LTL !).  He also said that the path from Houghton to Thunder Bay on 2m
> has enhancement from ducting A LOT.  I don't have any of that here, but
> hopefully, its where I can find it at home.
>
> There are WX buoys in Superior, plus C-MAN stations; see the link:
> <http://www.ndbc.noaa.gov/Maps/WestGL.shtml>   There is nothing for
vertical
> profile, however.
>
> The "over-the-water" ducting stuff is well known and documented around
the
> world.  I'd even heard of it, but always associated with warm water.
Lake
> Superior is NOT warm water, so I never thought the mechanism would work.
> Oh, well.  Another cherished belief proven wrong.
>
> One interesting thing in the stuff I found was that the depth of the
layer
> was corelated with wind speed.  Calm days produce a thinner layer than
windy
> days.  (Of course, TOO windy, and the layer is ripped apart.)  This would
> suggest to me that the ducting is triggered by moisture content... i.e.,
the
> more moist the air, the greater the refraction coefficient.  Low wind
days
> mean that evaporation is limited because the duct "seals" the surface,
> reducing evaporation.  With wind to stir things up, there is more
> evaporation possible, so the duct gets thicker.
>
> 73 Donn
> WA2VOI/0
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Sent: Monday, February 10, 2003 9:55 AM
> To: [email protected]
> Subject: [NLRS] Skew - T data for over Lake Superior
>
>
>
> I was taking with Bob,W0AUS, at our club breakfast last Sat. regarding 10
> GHz propagation over the Great Lakes and my thoughts once again turned
> toward "ducting" over that large body of pretty darn cold water and what
is
> going on.    We know that the 10 GHz group has shown on at least several
> occasions that height above the lake is detrimental to making the path
and
> that being located close to the water was important.   This would suggest
> some type of duct effect, or maybe a boundary layer.
>
> We do know that a refraction layer is created when you have warmer drier
> air over colder moist air and that the required duct thickness for
> propagation decreases with increasing frequency.   So, is Lake Superior
> with its very cold water capable of cooling the air right above it and
> providing moisture to that same air mass ?   Given that the lake is
pretty
> fixed in its physical characteristics, but the weather above it
fluctuates,
> are there better weather days to look for any ducts over the lake, like
> perhaps a warm dry day with little or no wind ?     A humid day may be
bad
> for duct forming in this case as it may neutralize any boundary.
>
> So, here is my question, is anyone aware of temperature & dew point data,
> or studies, for the summertime over the Great Lakes, preferably just the
> lowest 200 feet or so, with vertical resolution (data points) of 10's of
> feet ?    Best data would include air pressure, air temperature, and dew
> point for each vertical data point (just like the sounding balloons that
> the NWS puts up twice a day).
>
> 73, Jon
> W0ZQ
>
> _______________________________________________
> NLRS mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/nlrs
> _______________________________________________
> NLRS mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/nlrs

_______________________________________________
NLRS mailing list
[email protected]
http://mailman.qth.net/mailman/listinfo/nlrs