On 12/28/2015 9:59 PM, Snuffy "Hub Cap" McKinney wrote:
Yet you notice I saw a 20 degree rise in the course of a couple of minutes
by moving mine from the "sheltered porch" to the "open yard" 12 feet away?
I could actually *watch* the indicator move every few seconds!
20 degrees is not a trivial error!
Not if you put a little awning over them.
IIUC white on the top and black on the bottom, but any color will do
most of it.
The only diff. between the shady side of the house and the sunny side
is the shade!!
On Wednesday, December 30, 2015 at 2:04:12 AM UTC-5, Micky wrote:
The sun can heat up the surrounding area and surfaces and well as cause
evaporation, completely changing the "local" climate.
A "little awning" over a sensor to protect it from the sun is not going
to completely compensate for the temperature difference caused by the sun's
influence on the surrounding area.
Try a protected sensor over a sun drenched blacktop driveway and a protected
sensor over a sun drenched lawn or even a sun drenched pond. Tell me if
they report the same temperature.
On Wed, 30 Dec 2015 07:32:46 -0800 (PST), DerbyDad03
But then if that is happening near the tree, that is the temperature
near the tree.
The goal IS to measure the temperature of the surrounding area. All
the awning is for is to keep the direct sunlight from making the
thermometer too hot, as in Don's example of it reading 20 degrees
higher after he carried it in the bright sun for 20 feet.
With the driveway you'd probably have to protect it from heat
radiating from the blacktop. I assume his trees are planted in the
middle of a grassy area, or an area with other vegatation.
Of course not but it doesn't matter. The goal is to measure the
temperature by the trees, which is why you put the thermometer(s) by
| I'll often just touch the window to see how cold it feels to gauge how
| many layers of sweater and coat I need before going outside.
Hopefully you don't end up getting double
insulated glass. You could freeze to death. :)
You could blow an afternoon building a solar shield
or you could skip the tinkering and just go to ObamaWeather at
and punch in your local ICAO airport code.
Yeah, but in order to not ADD to the error, they tend to need
to be *large*, well vented, etc.
Ever hear of the term "microclimate"? :> The airport weather
ONLY applies to the airport, here. Different elevation, different
air flow (not wind!) patterns, etc. Every TV station reports
a different set of conditions, based on their *local* area
(which part of town).
Temperatures on the south end of our street (three blocks from here)
are 2 or 3 degrees warmer (Spring comes to them 2 weeks sooner
than for us -- as measured by when *their* flowers first bloom
In a small nearby town, there are 4 signs with the temperature. (2
banks, one gas station, and a community sign). NONE of them are ever the
same. They vary by as much as 6 deg. All of them are within one half
mile. I compared them to my cellphone weather, and the gas station is
always the most accurate (and it's also the newest sign). No thermometer
is 100% accurate.....
How about under the porch? In my case the deck off the kitchen is 8'
above the ground and the sensor is mounted below it, in the shade.
Proper position is 4" to 6" above ground and with good airflow.
To follow NWS standards it should be placed at a distance 4X the height
of the nearest structure, but that is impossible for most of us.
We're "at grade" so no "below" possible.
Current installation is on the back porch, a couple of feet below the
"roof"/ceiling -- high enough to be out of the way yet not so high
that I can't easily reach it with my outstretched arm.
This consistently reads warmer than "actual" -- because the roof and
house trap too much air (despite the porch/patio protruding out from the
house -- unobstructed on 3 sides).
I know this by comparing to another "thermometer" located out in the
middle of the yard (*that* one is useless during daylight hours as
it reads MUCH hotter than normal when the sun cooks it!).
There's only so much we can realistically do; can't deploy smudge pots
as there are too many structures nearby; can't deploy fans as the trees
aren't arranged in a "grove" (we'd need several small fans, instead).
We opt to cover the trees and use small heat sources to help encourage
convective air flow (has to work in case it's also raining).
I've covetously eyed the "blow up figures" that folks put out for
holiday decorations thinking that I might be able to repurpose the
fans used in them. They *should* be able to tolerate rain, right?
OTOH, they are covered by a large inflatable fabric sack so I'm
not sure how well they actually fare in a downpour! (do people
actually have them inflated when its raining??)
The more practical solution is to move to higher ground farther
from the wash.
Or, stop growing fruit that doesn't like the weather!! :>
[I've repeatedly threatened SWMBO that when the next REALLY cold
spell comes through and whacks the trees, I'll use them in the
smoker!! :> ]
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