This should help re NWS wx sensor siting. It is part of a message I received
from the then NWS Observation Program Team Leader. The NWS Directive does
not address anemometer siting but the PLT goes on to address this. Where NWS
or Oregon State Dept of Transportation has established sites in this state
it appears the significant majority of the anemometers are mounted around
the 10 M mark on top of small towers, typically in open exposed areas with
minimal nearby obstructions.
Don W7WLL
" The NWS directive for siting equipment is NWSI 10-1302. The link below
should take you to it, or you can do a Google search to find it.
http://www.nws.noaa.gov/directives/sym/pd01013002curr.pdf
The ideal spot to put weather equipment is in the middle of a flat
field, far from buildings, trees or pavement. Since this is unrealistic in
almost all situations, a compromise is usually necessary. The National
Weather service does not allow temperature and rain sensors on any rooftop.
The temperature sensor needs to be above a "natural" surface like grass or
dirt. It should be 4 to 6 feet above the ground and well away from trees and
buildings. My main concern is having a good airflow around the instrument
that is as free from disruptions as possible.
Rain gauges also can not be on a roof. Take the height of any
obstructions, double it and this is the distance they should be from the
sensors. This is usually difficult to achieve. Do the best you can. For
precipitation, a ring of trees or buildings about 100 feet from the gauge is
helpful. It breaks up the wind and allows precipitation to fall into the
gauge, rather than blowing against the side.
Wind sensors at airports are usually 10 meters tall (about 33 feet).
Since you don't live at an airport, this is hard to install. Also the
strong winds along the coast would twist all but the strongest of wind
towers. Do the best you can on height and minimize the upstream
obstructions. Place the wind sensor well above the height and buildings and
trees if possible for best readings."
-----Original Message-----
From: Hans Hammarquist via TowerTalk
Sent: Tuesday, September 01, 2015 5:39 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Fwd: weather station on tower?
Dave,
I believe that the "standard" require the wind to be measured at a 10 meter
elevation and the meter be surrounded by an open field. Your site would be
OK. Mine is not with all the surrounding trees.
There are several formulas how to "correct" a wind reading on other heights
but the knowledge I received (about 100 years ago) must have changed as I
didn't recognized it when i saw it last.
Hans - N2JFS
-----Original Message-----
From: David Robbins <k1ttt@arrl.net>
To: towertalk <towertalk@contesting.com>
Sent: Mon, Aug 31, 2015 6:07 pm
Subject: Re: [TowerTalk] weather station on tower?
Two things to consider... usb has a limited range, past a certain distance
you
need repeaters. I use a wired Davis station here and have no problem with
rf,
though I did put ferrites on the power cord and the usb cable to control box
that is right next to the computer anyway. The other is that if you are
reporting to noaa (I don't know if wu goes to them or not, I report via aprs
to
cwop which does go to noaa after filtering) they want anemometers at
certain
heights so they get consistent readings across an area.
David Robbins
K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster
node: 145.69MHz or telnet://k1ttt.net
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