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From: <Rick.Sylvia_at_ferguson.com>
subject: [Paddlewise] Taking Water Temps
Date: Fri, 5 Jul 2002 10:40:19 -0400
Hi all.  I recently got a cheapo $4 swimming pool / sauna thermometer.  I've been playing with water temps for the fun of it, but I'm not sure I'm getting good readings, so I want to ask you how you do it (for those who do).

Currently, I've got a lanyard attached to the thermometer, and I just drop it overboard and drag it along for about 10 minutes.  When I drag it, it's only about an inch underwater.  It's got holes in the top and bottom,  so it gets water flowing through it as it's dragged along.

Is that adequate?  How do you do it?

Rick - Poquosn, VA


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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Fri, 5 Jul 2002 11:55:20 -0400
From: <Rick.Sylvia_at_ferguson.com>

> Currently, I've got a lanyard attached to the thermometer, and I just drop it 
> overboard and drag it along for about 10 minutes.  When I drag it, it's only 
> about an inch underwater.  It's got holes in the top and bottom,  so it gets 
> water flowing through it as it's dragged along.

I've never done anything like this, but I will mention that moving the thermometer
will result in slightly different temperatures than keeping it still - think of 
wind chill.

As well, the water temperatures can change dramatically with depth.  The top layers
can be significantly warmer due to sunlight absorption, rainfall etc, and can be 
warmed or cooled by wind.  If you get more than a few inches down, the temp can
drop a lot - however, it may vary more slowly over time.  Therefore, measuring 
the temperature at the same depth is important if you want a realistic comparison 
from day to day.  Measuring the temp profile with depth can be interesting - 
attaching the thermometer to a knotted line and measuring at each knot each time 
will show how temps change with depth over time.  If you're on a boreal lake, you 
might even catch the seasonal turnover (I forget what that's called) if you 
measure year round.

Mike

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From: Rafael Mier Maza <sildriel_at_ciateq.net.mx>
subject: Re: [Paddlewise] Taking Water Temps
Date: Fri, 05 Jul 2002 15:35:03 -0500
>I've never done anything like this, but I will mention that moving the 
>thermometer
>will result in slightly different temperatures than keeping it still - 
>think of
>wind chill.
>
I may be wrong but I think the chilling factor has to do with the body 
loosing heat to try to maintain the surface temperature. The more wind the 
faster the surface is cooled down because there is more energy 
removed.  The chilling factor affects living mechanisms that fight to keep 
the surface temperature. A body may need to send out 500 calories for a 
given static temperature or the same for a higher temperature but with 
wind, the wind conversion to the equivalent static temperature is the 
chilling factor. A thermometer will measure the temperature of the water 
moving since it does not have internal energy to supply to keep the surface 
temperature at a give value. The only temperature change might be due to 
heating by friction against the water which I think  is so small that could 
be neglected.

Therefore I think the reading should be very accurate of the average 
surface temperature which in a moving lake should take care of a couple or 
three feet depth, and is close to the temperature a capsized individual 
might feel in his face and body.

As Mike says depending on the objective deeper measurements might be 
useful. I would be interested in teh close to surface temperatures anyway.

Best Regards,

Rafael Mier Maza
mayanseas.com




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From: Alex Ferguson <a.ferguson_at_chem.canterbury.ac.nz>
subject: Re: [Paddlewise] Taking Water Temps
Date: Mon, 08 Jul 2002 10:55:50 +1200
>I've never done anything like this, but I will mention that moving the 
>thermometer
>will result in slightly different temperatures than keeping it still - 
>think of
wind chill.

"Wind chill" effect would only happen if there was evaporation. What you 
should get theoretically is an increase in temperature due to friction of 
the thermometer moving through the water. At something less than a 1000 
knots you should be able to boil water shouldn't you??????

Alex
.
.

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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Fri, 5 Jul 2002 13:34:00 -0400
From: "Michael Daly" <michaeldaly_at_rogers.com>

> I've never done anything like this, but I will mention that moving the thermometer
> will result in slightly different temperatures than keeping it still - think of 
> wind chill.

I want to clarify this - there's a bias in my thinking where I think of the 
thermometer initially at air temp with air temp higher than water temp.
This need not be the case and the comment on wind chill might make you
think that the moving thermometer would record a colder temp.

The thermometer has to reach equilibrium with the water.  A moving thermometer
will reach equilibrium faster than one that is static, since the moving water
will either carry away heat (warmer thermometer) or add heat (colder thermometer)
more quickly.  If you take a temp reading quickly, a moving thermometer will be
more accurate.  If you leave it immersed long enough, it doesn't matter.

Since you are dragging it for 10 minutes, you're likely getting a good reading.
The problem of depth still remains.

Mike

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From: Joe Pylka <pylka_at_castle.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Fri, 5 Jul 2002 19:37:35 -0400
From: <Rick.Sylvia_at_ferguson.com>





> Currently, I've got a lanyard attached to the thermometer, and I just drop
it 


> overboard and drag it along for about 10 minutes.  When I drag it, it's only

> about an inch underwater.  It's got holes in the top and bottom,  so it gets

> water flowing through it as it's dragged along.





    Ten minutes could be overkill, but it depends on the mass of the
thermometer and how quickly it would reach equilibrium with the water.  


WRT depth, I think an inch is too shallow for nonmoving water.  Surface temps
can be appreciably higher on a lake than just a foot below.  If you have swum
in quiet water you'll have a sense of what I mean.  Moving water in a stream
can mix readily, so a surface temp might be representative.





    You might do either of two things.  Put a weight on the end of the
thermometer (maybe a coupla ounces) to keep it at a better depth, perhaps a
foot.  Alternatively (and I've done this on many occasions)  take a goodsized
mason jar and scoop up the water from a foot below and drop the thermometer in
it.  There won't be a significant temperature change for the length of time
that you'll need for the thermometer/water system to equilibrate.  --Done this
kind of thing many times when working out dissolved oxygen readings...  





Joe P.








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From: Bill Chitty <gwchitty_at_hotmail.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Fri, 5 Jul 2002 15:17:28 -0500
I think you are on the right track with the phenomena of the moving Vs  the
static thermometer.  To be more precise, the static thermometer is working
by conduction only.  The water in contact with the thermometer absorbs the
heat from the thermometer and lowers its temperature to the water
temperature while heating the water imperceptibly.  When you move the
thermometer you add convection to the cooling process and you are speeding
the cooling process of the thermometer.  All this assumes that the water is
at the same temperature everywhere you move it and maybe this should be
called an average temperature.

The process of wind chill is a different mechanism.  To really have wind
chill you need to be moving air over a thermometer that can evaporate water
off its surface continuously.  This would be the "wet bulb" temperature.
The cooling effect is augmented by the evaporation of the water out of the
wet cloth and the temperature measured is actually less than the temperature
of the air.  This also applies to your body, wind chill causes you to cool
by conduction, convection, and evaporation from your pores.

It is hard to say that wind chill affects things that are dry like your car
or your kayak on the roof.  I don't think there is a water chill effect.
Anyway, I'm ranting for no reason.  Towing the thermometer quickly produces
the same effect as holding it still provided all the water is at the same
temperature.  This makes me wonder why the weatherman gives us a "heat
index" in the summer but doesn't deduct for a wind chill factor?

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From: Jennifer Pivovar <kayak_at_headwinds.org>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 6 Jul 2002 03:17:04 -0700 (PDT)
--- Rick.Sylvia_at_ferguson.com wrote:
...I want to ask you how you do it (for those who do).
> 

Since I've been coordinating the PTFL, I take the
water temp at each launch (mainly to raise awareness
of how very cold our water can be even late in the
season).  I have a stream thermometer on a lanyard
with knots at 5' and 10' depths.  I paddle out from
the launch about 100 yards or so and stop, drop the
thermometer to depth, and sit for about 3 minutes. 
Haul the thing in quickly and read it before the air
can affect the temp.

The 5' depth is my target, the 10' is just for fun to
see the stratification in the water.  I figure in a
capsize you'll be sitting in the top 5' of water while
you try to get back in the boat, so that's what's
relevant for my purposes. 

I have tried to measure while under way, but as you
have noticed trolling with your thermometer only gets
you info on the top 2 inches.  Since I haven't figured
out how to stay at that level out of the boat it's not
real meaningful to me.  It depends on what you're
after.

Since I live on a large, deep (660') lake, it is
subject to "lake turns", where the water temps can
vary as much as 10-15 degrees F in a day's time when
the lake "turns".  Also, the direction of winds can
greatly affect the surface temps.  In my case, a
strong sustained wind from the north blows in warmer
surface water to my cove, where a sustained S-SE
pattern (typical) will result in a gradual drop in
temp over a couple days.  These surface changes are
only noticeable in the top 3-5 feet, the temp at 10'
stays relatively constant.

Enjoy,
Jennifer

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From: David Walker <dwalker_at_newwave.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 06 Jul 2002 09:49:25 -0700
Jennifer Pivovar wrote:

>
> Since I live on a large, deep (660') lake, it is
> subject to "lake turns", where the water temps can
> vary as much as 10-15 degrees F in a day's time when
> the lake "turns".

OK. I've taken the bait. What's a "lake turn" ? And why would a lake want to do
that sort of thing ?



regards,

David




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From: Brian Curtiss <bc_at_asdi.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 6 Jul 2002 10:56:08 -0600
>OK. I've taken the bait. What's a "lake turn" ? And why would a lake 
>want to do that sort of thing ?

Cooler water is more dense (actually, water is most dense at 4 deg C, 
decreasing in density when colder or warmer than this).  Thus, most 
lakes are stratified with a lower more dense, cooler layer (the 
hypolimnion) and an upper less dense, warmer layer (the epolimnion). 
The boundary between these two layers is called the thermocline.  The 
depth of the epolimnion grows during the warmer months.  The density 
gradient resists wind-induced vertical mixing (thing of layers of oil 
and water).  In the fall, the cooling of the epolimnion often results 
in the lake "turning over" --- this happens when the surface layer 
cools to the point where it is colder (read more dense) than the 
lower layer.  In cold climates, the cooling of the surface water in 
spring associated with ice melt can produce another turn-over --- 
water at the bottom of the lake will be near 4 deg C; the melting ice 
cools the surface water to near this temperature; the lack of 
temperature stratification allows a wind-induced turnover (there 
isn't much resistance to vertical mixing because of the lack of 
stratification).

See http://wow.nrri.umn.edu/wow/under/primer/page5.html  for a more 
detailed description.

Brian Curtiss

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From: Jennifer Pivovar <kayak_at_headwinds.org>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 6 Jul 2002 15:36:16 -0700 (PDT)
Thanks to Joe & Brian for doing a MUCH better job of
explaining this than I ever could!

Jennifer

--- David Walker <dwalker_at_newwave.net> wrote:
> 
> OK. I've taken the bait. What's a "lake turn" ? And
> why would a lake want to do
> that sort of thing ?
> 

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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 6 Jul 2002 23:39:31 -0400
From: "Jennifer Pivovar" <kayak_at_headwinds.org>

> I have a stream thermometer on a lanyard
> with knots at 5' and 10' depths. 

Where did you get these depths?  Were they arbitrary choices?

I did a quick search Friday on measuring water temperatures and couldn't
find a "standard" (I figured meteorologists would have one), however,
I did notice that 10 cm (4 inch) was commonly specified.  No idea why.

Mike

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From: Jennifer Pivovar <kayak_at_headwinds.org>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 03:08:53 -0700 (PDT)
--- Michael Daly <michaeldaly_at_rogers.com> wrote:
> > with knots at 5' and 10' depths. 
> 
> Where did you get these depths?  Were they arbitrary
> choices?...

Hi Mike,

I didn't mean to imply they were standard.  I think
'standard' depends on the purpose.  As I noted, the 5'
depth is due to the fact that in a capsize you're
going to be in the top 5' of water while you recover,
so that's what I was interested in measuring.  The 10'
is just for fun to see the difference.  I think 4" is
too shallow to give an accurate picture of what you'll
encounter out of the boat, but I may be all wet :).

I'm sure the USGS has some standard for their stream
guages, but I haven't checked yet.

Off to paddle Canandaigua .....
10-15 K NW breezes, 85 deg F air, 72 deg F water temp,
Sunshine.... wish you could all be here

Jennifer

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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 13:25:48 -0400
From: "Jennifer Pivovar" <kayak_at_headwinds.org>

> --- Michael Daly <michaeldaly_at_rogers.com> wrote:
> > > with knots at 5' and 10' depths. 
> > 
> > Where did you get these depths?  Were they arbitrary
> > choices?...
> 
> I didn't mean to imply they were standard.  

I didn't think they were, but I thought you might have got them
from someone else who had a reason based on some standard for
a club or organization.

> I think 4" is
> too shallow to give an accurate picture of what you'll
> encounter out of the boat, but I may be all wet :).

Four inches is around the depth that I notice a change from
warm surface water to colder lake water in many still lakes.  
I can see it being useful in a turbulent stream where there
is little temperature stratification, but in lakes it would be
next to useless.

I wonder if two foot depth would be better for reflecting the 
depth at which a paddler would be affected - five foot would
be at their toes; two foot, at their waist.

> I'm sure the USGS has some standard for their stream
> guages, but I haven't checked yet.

They must have.  Does NOAA have offshore weather bouys with temperature
readings?  I was paddling yesterday within sight of the following bouy
on southern Georgian Bay:

http://weatheroffice.ec.gc.ca/scripts/marinegen.pl?Client=ECMar_e&city=45143

The water was warm to a considerable depth compared to what I expect in the 
more northerly areas of Georgian Bay.  The recorder temp was 17C but it felt
much warmer where we were closer to shore.

Mike

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From: Kevin Zembower <kevinz_at_fellspt.charm.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Mon, 8 Jul 2002 09:46:37 -0400 (EDT)
I'm wondering why none of the 'gearheads' in this group have mentioned a
remote sensing electronic thermometer. Radio Shack (here in the US) sells
a cheap one with a 5 or 6 foot wire to the remote sensing element for
under $10 USD and one that 'speaks' the temperature for under $20. A lead
fishing weight for the remote element and you've got an instrument good to
a tenth of a degree, C or F that you can read accurately while underway.

You would, however, need to make some waterproofing modifications. I just
thought of the last rolling/rescue practice I attended at the Chesapeake
Paddler's Association in Annapolis, MD. I had my house and car keys tied
inside my PFD. When I got home, I noticed the Princeton Tec pulsar light,
powered by two small coin batteries, glowing weakly. I couldn't turn it
off. When I took it apart, there was a tremendous amount of corrosion on
the batteries, due to electrolysis in the brackish water we were in. Then
I remembered another paddler who noticed that her car key would still
unlock her car, but that she couldn't turn off the burglar alarm. It
wasn't until I got home that I remembered that, and then thought that her
car key also had a battery for the car alarm turn-off transmitter.

-Kevin Zembower

--
  kevinz_at_charm.net      Kevin Zembower

On Sat, 6 Jul 2002, Jennifer Pivovar wrote:

> --- Rick.Sylvia_at_ferguson.com wrote:
> ...I want to ask you how you do it (for those who do).
> >

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From: Joe Pylka <pylka_at_castle.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 6 Jul 2002 12:29:49 -0400
>>>OK. I've taken the bait. What's a "lake turn" ? And why would a lake want
to do


that sort of thing ?


regards,


David





  It's part of the annual cycle of water in a large, mostly deep, lake.  The
word is "Turnover".  As the weather warms and winds blow, the upper surface of
a lake gets moved and heated.  Sooner or later currents will set up in the
upper layers from one side of the lake to another.  This circulation tends to
keep the accumulated heat and sediments, plankton, oxygen, etc. in that upper
layer.  The transition between the upper and lower layer is called the
"Thermocline", a stratum where the temperature drops abruptly.  Ever swim in a
lake in nice warm temps then tread water and get your feet into something
really cold?  You just punched through the thermocline.  


    The upper water cools as autumn/winter approaches, and at some point this
thermocline barrier breaks down and the upper and lower layers mix; fairly
abruptly and thoroughly.  That's the Turnover.  


    Check out a couple of texts on Limnology -- that's the science of water
ecosystems.  Much better descriptions than mine are available.  Some general
Ecology textbooks describe this as well.





Joe P.

















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From: David Walker <dwalker_at_newwave.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sat, 06 Jul 2002 23:26:17 -0700
Joe Pylka wrote:

>
>
>   It's part of the annual cycle of water in a large, mostly deep, lake.
>
>     The upper water cools as autumn/winter approaches, and at some point this
> thermocline barrier breaks down and the upper and lower layers mix; fairly
> abruptly and thoroughly.  That's the Turnover.

Thanks Joe and Brian for the explanation. I suspected that dynamic from  season to
season . What threw me was when Jennifer said "Since I live on a large, deep
(660') lake, it is
subject to "lake turns", where the water temps can vary as much as 10-15 degrees F
in a day's time when the lake "turns"."  So I couldn't understand how the water
could mix from top to bottom over a 24 hour period . At least not to a great
extent. But I suppose there is some turning or turnover in the upper layers of the
water between sun rise to sun rise going from a hot sunny day to a cool night air
with the complete turn over from summer to winter .

I often paddle on a local lake where I think the maximum depth is around 400 feet
in the main part of the lake so I was well aware that the water temps drop
dramatically only a few feet down.

Regards,

David


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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 13:46:22 -0400
From: "Michael Daly" <michaeldaly_at_rogers.com>

> Does NOAA have offshore weather bouys with temperature readings?  

I should have checked myself - they do, lots!  

And I found this on the NOAA web site:

"Sea surface temperature sensors are located at a depth of 1.5 meters 
for 10-m and 12-m buoys and at 1 meter for all 3-m and 6-m moored buoys"

So the big bouys measure at five foot depth and the smaller ones at
a bit over three foot.

What I found interesting in searching for the same info from Environment
Canada was that the Canadian network of bouys are in the Atlantic and
Great Lakes but none are located in the Pacific waters.  Hey Doug! Don't
you guys pay taxes? :-)

Mike



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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 20:58:53 -0400
From: "Alex Ferguson" <a.ferguson_at_chem.canterbury.ac.nz>

> "Wind chill" effect would only happen if there was evaporation. 

Around here, wind chill is only reported in the winter, when perspiration
can be negligible.  Wind chill is based on heat transfer from skin to air.  
(I was interested to find out that the new wind chill model was verified 
at DCIEM, a few kilometers north of where I live).

Mike


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From: WhiteRabbit <whiterabbit_at_empowering.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 21:24:11 -0500
Instead of wind chill the proper term is wet bulb depression.   As water
evaporates from the thermometer bulb it cools the bulb (heat of
vaporization).  Unless you are using an very sensitive instant read
thermometer, the effect is negligible.    The thermal effect of water that
evaporates is small relative to the thermal mass of the bulb.

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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Sun, 7 Jul 2002 23:27:24 -0400
From: "WhiteRabbit" <whiterabbit_at_empowering.com>

> Instead of wind chill the proper term is wet bulb depression.   

These are two very different phenomena.  

Wind chill refers to the transfer of heat from skin to air - the 
more air flow, the greater the heat removal.  Wind chill temperatures
are calibrated to show the equivalent temperature of still air.
My analogy to the effect of water flow is reasonable.

Wet bulb temperatures indicate the effect of evaporation on apparent 
temperature - this also is affected by relative humidity, I think.

A number of folks have commented on evaporation and wind chill - I wonder
if other regions/countries use a definition different than that used in 
Canada and the US?

Mike

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From: Dave Kruger <dkruger_at_pacifier.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Mon, 8 Jul 2002 08:51:24 -0700
Michael Daly" <michaeldaly_at_rogers.com> wrote:
Subject:

From: "Michael Daly" <michaeldaly_at_rogers.com>

>> Does NOAA have offshore weather buoys with temperature readings?  [yes]

>> What I found interesting in searching for the same info from Environment
Canada was that the Canadian network of buoys are in the Atlantic and
Great Lakes but none are located in the Pacific waters.  Hey Doug! Don't
you guys pay taxes? :-) >>

Definitely there are similar buoys in offshore Canadian waters. Maybe not on
Web sites, though.  There is a ring of maybe five or six around the Queen
Charlottes, and their observations are reported (via computer "voice") on the
VHF weather channel, updated every hour or so.  Invaluable info for detecting
passage of a front, and for sea state values.

May not have water temp capability.  Can't remember.

--
Dave Kruger
Astoria, OR

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From: Eric Unrau <eunrau_at_yahoo.ca>
subject: RE: [Paddlewise] Taking Water Temps
Date: Mon, 8 Jul 2002 09:27:50 -0700
Most of the Pacific Marine Weather Buoys report sea temperature.  Just
click on the red triangles on the following pages:

http://weatheroffice.ec.gc.ca/natmarine/bc/georgiabasin_e.html
http://weatheroffice.ec.gc.ca/natmarine/bc/south_coast_e.html
http://weatheroffice.ec.gc.ca/natmarine/bc/north_coast_e.html



~~Eric~
Vancouver, BC


> -----Original Message-----
> 
> >> Does NOAA have offshore weather buoys with temperature readings?
[yes]
> 
> >> What I found interesting in searching for the same info from
> Environment
> Canada was that the Canadian network of buoys are in the Atlantic and
> Great Lakes but none are located in the Pacific waters.  Hey Doug!
Don't
> you guys pay taxes? :-) >>
> 
> Definitely there are similar buoys in offshore Canadian waters. Maybe
not
> on
> Web sites, though.  There is a ring of maybe five or six around the
Queen
> Charlottes, and their observations are reported (via computer "voice")
on
> the
> VHF weather channel




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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Taking Water Temps
Date: Mon, 8 Jul 2002 13:48:26 -0400
From: "Eric Unrau" <eunrau_at_yahoo.ca>

> Most of the Pacific Marine Weather Buoys report sea temperature.  Just
> click on the red triangles on the following pages:
> 
> http://weatheroffice.ec.gc.ca/natmarine/bc/georgiabasin_e.html
> http://weatheroffice.ec.gc.ca/natmarine/bc/south_coast_e.html
> http://weatheroffice.ec.gc.ca/natmarine/bc/north_coast_e.html

Oops - now I get it - the Pacific information is buried another level
deeper in the web pages for the Pacific.

Mike

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From: Steve Holtzman <sh_at_actglobal.net>
subject: Re: [Paddlewise] Taking Water Temps
Date: Mon, 8 Jul 2002 11:00:17 -0700
Does that mean that you East Coast types are "shallower" then us Correct
Coast types??

Steve

From: "Michael Daly" <michaeldaly_at_rogers.com>



> Oops - now I get it - the Pacific information is buried another level
> deeper in the web pages for the Pacific.



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