Question about temperature measurements

In summary: MI/InstrumentShelter.htm Used in measured highs/lows/hourly temperatures, shade temperatures are generally cooler than temperatures under direct sunlight. A temperature measurement under direct sunlight will only tell you the temperature of the thermometer itself, not the air temperature. When official measurements are taken about 1.5 meters above the ground, in a white shelter that is ventilated at a certain rate, the ventilation keeps the air mixed and fresh (think greenhouse effect, or lack thereof). However, this can lead to problems, such as the white color of the shelter deteriorating over time.
  • #1
Simfish
Gold Member
823
2
Used in measured highs/lows/hourly temperatures.

Are they shade temperatures or temperatures under the Sun? Also - are shade temperatures really cooler than temperatures under the Sun?
 
Earth sciences news on Phys.org
  • #2
Yes, they are shade temperatures, and yes, these are often much lower than a reading under direct sunlight. A temperature measurement under direct sunlight will only tell you the temperature of the thermometer itself, not the air temperature.
 
  • #3
http://www.rickly.com/MI/InstrumentShelter.htm
 
Last edited by a moderator:
  • #4
When I was in high school, they used to call those things Stevenson Screens.
 
  • #5
All official measurements are taken about 1.5 meters above the ground, in a white shelter that is ventilated at a certain rate. The white color (ideally) gives the shelter a very high albedo, close to 100%, which means that it won't absorb sunlight and warm up... the ventilation keeps the air mixed and fresh (think greenhouse effect, or lack thereof).

Unfortunately, this can lead to problems... you can imagine that shelters don't stay perfectly white throughout their existence, for instance.
 
  • #6
Weather Freak said:
All official measurements are taken about 1.5 meters above the ground, in a white shelter that is ventilated at a certain rate.

What rate is that? When was such a specification added? How are "corrections" made for "unventilated" data collected prior to that time?

For the record, there is no ventilation rate specified; there are forced ventilation shelters available, but they are not in common use.

The white color (ideally) gives the shelter a very high albedo, close to 100%, which means that it won't absorb sunlight and warm up... the ventilation keeps the air mixed and fresh (think greenhouse effect, or lack thereof).

"100%?" "Certain conditions and restrictions apply. Substantial penalties for early withdrawal, or in other random events." This is for chalk, clay, lead, or titanium whites? Oil, resin, lacquer, enamel, or latex bases? 5800 K emissivities run 0.1 - 0.3; 300 K emissivities run 0.6 - 0.8; temperature rises can get to 5 - 10 K in still air.

Unfortunately, this can lead to problems... you can imagine that shelters don't stay perfectly white throughout their existence, for instance.

Meteorological temperatures are NOT true air temperatures; they are a combination of true air temperature and wind speed.
 

FAQ: Question about temperature measurements

1. What is the most accurate way to measure temperature?

The most accurate way to measure temperature is with a thermometer that is calibrated to a known standard, such as the International Temperature Scale of 1990 (ITS-90).

2. Can temperature be measured without a thermometer?

Yes, there are other methods for measuring temperature such as using thermal imaging cameras or thermistors.

3. How does the temperature measurement affect scientific experiments?

Temperature is an important factor in many scientific experiments as it can impact the behavior of materials and chemical reactions. Accurate temperature measurements are crucial for obtaining reliable and repeatable results.

4. What is the difference between Celsius and Fahrenheit temperature scales?

Celsius (°C) and Fahrenheit (°F) are two different units of temperature measurement. The Celsius scale is based on the freezing and boiling points of water, with 0°C being the freezing point and 100°C being the boiling point. The Fahrenheit scale is based on the freezing and boiling points of a mixture of ice, water, and salt, with 32°F being the freezing point and 212°F being the boiling point.

5. How does altitude affect temperature measurements?

As altitude increases, the air becomes less dense and the temperature decreases. This is because the air molecules are more spread out and have less energy, resulting in lower temperatures. Therefore, temperature measurements at higher altitudes may be lower than those at sea level.

Similar threads

Back
Top