[TowerTalk] Fwd: weather station on tower?

[Don W7WLL]

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 at 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 at arrl.net>
To: towertalk <towertalk at 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 at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster
node: 145.69MHz or telnet://k1ttt.net





_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk