[wxqc] Opinions please -- New design for solar radiation shielding

[Thomas Giella KN4LF]

Hi Bryce,

I tried that design 20 years ago and it worked fairly well with forced 
aspiration but shortwave radiation and precipitation entry was a problem at 
certain times of the year. I ended up using a white plumbing PVC tee and a 
couple of 45 degree elbows and that kept shortwave radiation and 
precipitation out. For ventilation I used a DC 45 cfm computer type muffin 
fan, with the fan sucking fresh air in from the front and passing across the 
sensors before reaching the fan. This design worked as good as my louvered 
Stevenson Screen.

BTW the bottom of the shelter should be 4-5 feet above ground level.

Take Care,
Thomas Giella, KN4LF
Retired Meteorologist
Lakeland, FL, USA
kn4lf at earthlink.net

Lakeland, Florida Daily Climatological Weather Data Archive: 
http://www.kn4lf.com/kn4lf22.htm
Lakeland, Florida Real Time Weather Observations: 
http://www.kn4lf.com/index1.html
Harmful Man Induced Climate Change (Global Warming) Refuted: 
http://www.kn4lf.com/globalwarminglie.htm
FL/US Raw Weather Forecasting Resource Links: 
http://www.kn4lf.com/kn4lf13.htm
New Scientific Evidence for the Existence of God: 
http://www.cosmicfingerprints.com/audio/newevidence.htm

After reading all the material that the CWOP program references about solar
radiation shields I had a brainstorm for a different design.

In essence it is a six inch pipe, open at either end, with the pipe set at
an angle such that it is oriented on a North/South plane with the north end
higher than the south end. Both ends of the pipe are cut at angles so that
no sun is able to enter the bottom half of the pipe regardless of the
seasonal angle of the sun's ecliptic. I used nylon screws to mount the
instruments to the inside of the pipe to prevent heat transmission from the
outside of the pipe through the screws.

Take a look at the Flickr images on
http://weather.gladstonefamily.net/site/C7166  to see how my prototype is
constructed and to make sense of the above description.

The thinking is, that because the north end of the pipe is elevated we will
get a chimney effect of the warmer air rising upward at the North end and
the cooler air "falling" out the south end of the pipe. The theory is that
there is very little chance of air stagnating in this configuration.

One thing I noticed right away is that the temperature and humidity seems
much more dynamic (or in other words, more changes during a given time
frame) which seems to indicate that I am indeed reducing the incidence of
air stagnation I was seeing with a gill style solar shield.

The one down side I see right now is that a driving rain from the North
might get the instrument package wet. I will have to create some kind of
barrier or hood that will not interfere with the convective flow. The nice
thing is that I believe this can remain passive (not fan aspirated) even
during the worst of the Arizona heat, we will see this summer.  I do notice
some slightly higher temps during the day, but they are not the same thing I
was seeing when I had a solar radiation problem. I would attribute that to
the microclimate of being between Stucco houses, with cinder block fences
and tile roof in proximity to the sensor.

If anyone wants to go back into my historical data I added the shield on
April 21 and tweaked my humidity about four days ago.

Let me know what you think, I welcome any suggestions or comments, positive
or negative.