[wxqc] dew point errors

[Ken Whelan]

Take a look at my station and its location.   CW5627.   It is sitting on
my boat dock on Beaver lake about 25' in the air.  Its only been
operational for about the last month or so.    As you can tell from
looking at the topo,   it is sitting in a pretty good valley.   The
reason for this placement is I want the windspeed and temperature on the
lake.   I am also pulling the water temperature based on an extra temp
sensor.
 
For me,  I have dewpoint errors when there is not much wind.    If there
is a good steady breeze the dewpoint(humidity) holds quite well with
other stations in the area.     The Humidity isn't much different up at
the house,  (about 120 yards up a hill) than it is on the dock.   The
reason for this is that the whole valley tends to have a higher
humidity.   Think of the mornings when you are on top of a hill and you
look out and see fog sitting in all the valleys around you.   We have
that occurance pretty regularly in my area, and my house is one of the
ones under the fog bank.   
 
What I am saying,  is to determine if the lake or perhaps your trees
holding the moisture near your sensors,  watch and see if your errors
are worse on days with no wind.   That will help you determine if you
have a sensor problem or not.
 
 
Please take what I have said here with a grain of salt as I am new to
this weatherstation thing myself.
kw

________________________________

From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net] On Behalf Of Bill Simm
Sent: Monday, April 17, 2006 12:35 AM
To: wxqc at lists.gladstonefamily.net
Subject: [wxqc] dew point errors


Hi there,
   I have been that getting out of range error message regarding my dew
point continuously for the last couple of weeks.   I thought maybe the
problem was the snowmelt,  but the last of the snow in yard dissapeared
about 2 weeks ago and I am still getting the error message. 
   My thermo-hygrometer is located on the north side of the shed right
on the corner (not directly under the eev - the shed is painted white).
There are also the two 120 foot spruce trees in the yard.  The result is
the thermo-hygrometer is not exposed to much direct sunlight.   The
instrument has its own litte wind and sun shield on it.  I think the
location is pretty good and combined effect of the all these conditions
pretty much amounts to being in a stevenson screen.      
   I am wondering if the problem has to do with my close proximity to
Cresent Lake?  If you are familiar with Portage la Praire,  you know
there is an oxbow lake in the centre of town.  (It was once part of the
Assignaboine River).    My weather station is about 100 meters from the
water.  
    There are two weather other stations in this area. One,  a CWOP
station at 
Southport (also an Enviroment Canada wx station) it is about 5 kms south
of Portage and not near any bodies of water.   The other is an
Enviroment Canada station at the University of Mantoba Field station in
the marsh at Delta beach along the shore of  Lake Winnipeg about 20 km
north of Portage La Praire.    
    Although close to me neither of these stations are good choice to
compair dew point or humidity readings with.    There are a bound to be
significant differances in our dew point and humidity readings due to
the proximity of  or lack of proximity of large or small bodies of water
to each station.     
    I would be very interested in hearing the opinion of anyone else
regarding my dew point error problem as indicated by the weather quality
report.
 
                                        Many thanks,
                                                                Bill
   
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