Author Topic: What is best method for measuring High temperatures in Hot climates ?  (Read 449 times)

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Offline heatseeker

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Seeking opinions on the best method to measure High temperatures in Hot climates.

Take Death Valley and Dalol, Ethiopia, two of the hottest spots on the planet.

Many weather stations incorporate a platinum resistance temperature sensor inside a ventilated weather shield, sometimes called a solar radiation shield.

An example is the CS 215 by Campbell Scientific.

That shield must act like a miniature oven in direct sunlight. 

I mean at 40 C in direct sunlight in a desert, how could we expect an accurate reading ?

Would not a thermometer in the shade of a building provide a more accurate reading during heat of the day ?
« Last Edit: February 19, 2022, 10:08:50 PM by heatseeker »

Offline CW2274

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #1 on: February 19, 2022, 10:56:20 PM »
That shield must act like a miniature oven in direct sunlight. 

I mean at 40 C in direct sunlight in a desert, how could we expect an accurate reading ?

Would not a thermometer in the shade of a building provide a more accurate reading during heat of the day ?
Ambient temperature is meant to be taken in direct sunlight with a quality radiation shield, passive or aspirated. I've been taking very accurate temps well above 40C for 14+ years in direct sun, sunup til sundown, as well as many others. All official temps are also taken in direct sun.

Offline Mattk

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #2 on: February 19, 2022, 10:58:35 PM »
Depends on exactly what temperature it is you want to measure?

- Direct affect of sunlight then put it out in the direct sun
- Temperature affected by heat induction and variability from a building then stand beside a building
- Air temperature (proper) then use a Stevenson Screen, this is what it is designed for

Simplistic so called PWS solar radiation shields are in no way equiv to a Stevenson Screen
 

Offline CW2274

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #3 on: February 19, 2022, 11:02:16 PM »
Simplistic so called PWS solar radiation shields are in no way equiv to a Stevenson Screen
Depends on what you classify as "simplistic". Their are many non Stevenson shields that are just as good if not better.

Offline heatseeker

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #4 on: February 19, 2022, 11:46:10 PM »
re radiation shields:  what's the difference between passive and aspirated ?

Offline CW2274

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #5 on: February 20, 2022, 12:13:38 AM »
A passive shield relies solely on wind to ventilate it. As long as there is some wind, a good passive shield is very effective. An aspirated shield uses a fan to draw a constant flow of ambient air across the sensor making wind speed irrelevant.

Offline DaleReid

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #6 on: February 20, 2022, 08:59:25 AM »
I don't know if it is commercially available yet, but recall a newly developed paint within the last couple years which is so reflective that it does not get the enclosed space warmer than ambient, even in direct sunlight. 

I'll have to go looking to see the name and if or when it might become available.

The Kitt Peak Solar Observatory about 60 miles west of Tucson has a long exposed structure to keep the optical path cool from the giant mirror at the top reflecting down into the instruments.  I recall it had a sort of odd color, and the information on the self guided tour said that the special formulation had titanium as part of the ingredients to keep it cool.

Ocala might have more info, but when I toured Cape Canaveral, it was remarkable how much the structures and piping above ground was getting weathered and beat up by the elements, including the sun.

I was impressed by carports at some of the hospitals in the Scottsdale area, and indeed walking out of the sun into the area under the metal shield, which was giving about 6 or 8 feet of clearance above the car and open on all sides, attested to the shielding.  Ambient air for some distance around would be influenced only by the surrounding microclimate of the sun exposure.  Rain sensors, if needed, could be located well outside that large shield.  Not practical for a back yard necessarily, but we're talking Sonoran or Mojave Deserts, and if the project were to do it right, I'd opt for some secondary shielding and free air flow through.

Cats seek out sunlit patches on the carpet during the winter, so there IS energy in sunlight. 
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Offline 1davidbrock

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Re: What is best method for measuring High temperatures in Hot climates ?
« Reply #7 on: February 26, 2022, 02:30:26 PM »
I don't know if it is commercially available yet, but recall a newly developed paint within the last couple years which is so reflective that it does not get the enclosed space warmer than ambient, even in direct sunlight. 

I'll have to go looking to see the name and if or when it might become available.

https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..html

https://pubmed.ncbi.nlm.nih.gov/33856776/
« Last Edit: February 26, 2022, 02:34:26 PM by 1davidbrock »
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