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Temperature (and humidity) measurement: Difference between revisions
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Temperature (and humidity) measurement (view source)
Revision as of 19:49, 31 July 2021
, 19:49, 31 July 2021→How Cumulus software handles Temperature and Humidity
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Temperature scales use a unit called degrees apparently because some early thermonmeter designs were based on circular tubes containing liquid and had 360 equally spaced markings on them as a rough way of reporting relative 'temperatures' before any formal scales based on calibrated points was introduced. | Temperature scales use a unit called degrees apparently because some early thermonmeter designs were based on circular tubes containing liquid and had 360 equally spaced markings on them as a rough way of reporting relative 'temperatures' before any formal scales based on calibrated points was introduced. | ||
==Fahrenheit== | ==Fahrenheit== | ||
Daniel Gabriel Fahrenheit (24 May 1686 to 16 September 1736) visited Ole Remer in 1708. In 1709 Fahrenheit originated the alcohol-in-glass thermometer, and in1724 Fahrenheit developed the scale named after him based on 3 fixed points (a slightly modified version of this scale still called Fahrenheit is still used by some people in UK and is the official scale in | |||
This remains the official scale to use in just one nation - the USA. | |||
Daniel Gabriel Fahrenheit (24 May 1686 to 16 September 1736) visited Ole Remer in 1708. In 1709 Fahrenheit originated the alcohol-in-glass thermometer, and in1724 Fahrenheit developed the scale named after him based on 3 fixed points (a slightly modified version of this scale still called Fahrenheit is still used by some people in UK and it is this modified scale that is the official scale in United States). | |||
== Rankine == | |||
Rankine is the name given to a scale starting at absolute zero (similar to Kelvin, but based on scale divisions that match Fahrenheit ones). | Rankine is the name given to a scale starting at absolute zero (similar to Kelvin, but based on scale divisions that match Fahrenheit ones). | ||
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The history of Celsius is confusing. | The history of Celsius is confusing. | ||
INTERNATIONAL STANDARD: The international standard scale for temperature measurements in the weather context is Celsius (after the Swedish person Anders Celsius 1701 to 1744) and defined internationally by two points - absolute zero (-273.15 degrees Celsius - the start of the Kelvin temperature scale) and the triple point of purified water (0.01 degrees Celsius). | INTERNATIONAL STANDARD: The international standard scale for temperature measurements in the weather context is Celsius (after the Swedish person Anders Celsius 1701 to 1744) and defined internationally by two points - absolute zero (-273.15 degrees Celsius - the start of the Kelvin temperature scale whose scale divisions match Celsius) and the triple point of purified water (0.01 degrees Celsius). | ||
ANDERS CELSIUS SCALE: Anders defined 0 on his Celsius scale as the boiling point of water and 100 on his scale as the freezing point of water. Carolus Linnaeus (1707 to 1778) in 1744 (after the death of Anders Celsius) reversed that Celsius scale, to the order we know now. Various other people are also credited with developing what was known under various names and became known in the 19th Century as the Centigrade scale. | ANDERS CELSIUS SCALE: Anders defined 0 on his Celsius scale as the boiling point of water and 100 on his scale as the freezing point of water. Carolus Linnaeus (1707 to 1778) in 1744 (after the death of Anders Celsius) reversed that Celsius scale, to the order we know now. Various other people are also credited with developing what was known under various names and became known in the 19th Century as the Centigrade scale. | ||
CENTIGRADE: Zero Centigrade is the freezing point of water and 100 units from there is water's boiling point at a pressure of one standard atmosphere. Jean-Pierre Christin in 1743 independently developed a temperature scale with zero for water's freezing point and 100 for water's boiling point and in May of that year he published the design of a thermometer by a craftsman in Lyon using this scale. The temperature scale 'in 100 steps' or in Latin 'centum gradus' (anglicised as Centigrade) officially ceased to exist in 1948, when the unit became degrees Celsius. | CENTIGRADE: Zero Centigrade is the freezing point of water and 100 units from there is water's boiling point at a pressure of one standard atmosphere. Jean-Pierre Christin in 1743 independently developed a temperature scale with zero for water's freezing point and 100 for water's boiling point and in May of that year he published the design of a thermometer by a craftsman in Lyon using this scale. | ||
*The temperature scale 'in 100 steps' or in Latin 'centum gradus' (anglicised as Centigrade) officially ceased to exist in 1948, when the unit became degrees Celsius. | |||
*This terminology is not used in the Spanish- and French-speaking world where grad applies to angular measurement (and centigrade is equivalent to 0.009 angular degrees - angular degrees is the unit where 360 is one rotation). | |||
*Older people still use the term Centigrade sometimes in the temperature measuring context. | |||
*Centigrade is often quoted by TV journalists, in the UK anyway, despite them being born after 1948! | |||
=Instruments= | =Instruments= | ||
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A more advanced model considers the density of the roughness, and for lots of tightly packed buildings (or trees), uses a bigger clearance (height or horizontal separation). (See [http://www.rmets.org/weather-and-climate/observing/guidelines-observing-0 Royal Meteorological Society website] in UK, [http://www.bom.gov.au/climate/how/observations/airtemp-measure.shtml BOM temperature measurement advice] in Austrailia, or the equivalent of a Meteorological Bureau for your country). | A more advanced model considers the density of the roughness, and for lots of tightly packed buildings (or trees), uses a bigger clearance (height or horizontal separation). (See [http://www.rmets.org/weather-and-climate/observing/guidelines-observing-0 Royal Meteorological Society website] in UK, [http://www.bom.gov.au/climate/how/observations/airtemp-measure.shtml BOM temperature measurement advice] in Austrailia, or the equivalent of a Meteorological Bureau for your country). | ||
=Cumulus Calculated Parameters= | =How Cumulus software handles Temperature and Humidity= | ||
Cumulus expects all stations to report a minimum number of parameters including outside temperature and relative humidity. Some weather station types also report wind chill, dew-point temperature, and other derivatives related to temperature and/or relative humidity. Cumulus is able to calculate wind chill, dew-point, and other derivatives (and if any of these are available from your station, you can choose whether to use the value from station or the value Cumulus calculates). | |||
If Cumulus (1 or MX) is using "outside temperature" in a calculation of parameters like dew-point, or apparent temperature, then for most stations it will apply any calibration settings to the temperature read from the station before using it in that calculation. In Cumulus 1, uncalibrated temperature values are used from Instromet, see support forum for more details. | |||
Similarly if humidity is read from the station, the calibrated value is used in subsequent calculations. See the support forum for further information e.g. '''for Instromet stations''', Cumulus 1 ''calculates the relative humidity from the reported wet bulb, and dry bulb'', temperatures, the uncalibrated values of temperature and (calculated) humidity are then used to calculate dew-point. | |||
== Logged values == | |||
At the logging interval you set, Cumulus logs outdoor temperature, dew-point, and relative humidity; plus a whole host of values derived from them (and from wind speed), in [[Standard_log_files]], with separate files for each month. | |||
Optionally, measurements from extra sensors can be logged in [[Extra_Sensor_Files| extra monthly files]]. For Oregon Scientific stations, temperature readings from one extra sensor can optionally replace the main sensor for "outdoor temperature", see [[Webtags#Web_tags_mentioning_.28outside.29_temperature|here]]for details. | |||
Optionally, but only in Cumulus 1, indoor measurements can be logged in [[speciallog.txt|a special ongoing log]]. | |||
From release 3.12.0, MX maintains a [[Cumulusmx.db|database table]] that can hold temperatures at one (assuming MX has been left running) minute intervals for the last 7 days. | |||
==Cumulus Calculated Parameters== | |||
See external Wiki or other sections of this Wiki for specific information on the values that Cumulus calculates: | See external Wiki or other sections of this Wiki for specific information on the values that Cumulus calculates: | ||
[http://en.wikipedia.org/wiki/Wet_bulb Wet bulb | [http://en.wikipedia.org/wiki/Wet_bulb Wet bulb] | ||
and [[#How_does_Cumulus_know_the_height_of_the_cloud_base.3F]] | |||
*The dew point calculation for Cumulus 1 uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)''' | |||
* The dew point calculation for MX follows the standard [https://en.wikipedia.org/wiki/Dew_point calculation in wikipedia] | |||
<pre>public static double DewPoint(double tempC, double humidity) | |||
{ | |||
double lnVapor = Math.Log(ActualVapourPressure(tempC, (int) humidity)); | |||
return ((243.12 * lnVapor) - 440.1) / (19.43 - lnVapor); | |||
}</pre> | |||
Note this means that Cumulus 1 and MX log files have a continuity break in dew point values when you migrate from one flavour to another. | |||
[[Apparent temperature]] and [[ | Look up [[Humidex]], [[Wind chill]], [[Heat index]], [[Apparent temperature]], [[Feels Like|Feels Like temperature]], [[Heat/cold degree days and Chill hours]], [[Average temperature]], | ||
[[Extra_Sensor_Files|Extra temperatures]] for details about the various derivatives. | |||
[[Category:Terminology]] | [[Category:Terminology]] | ||
History: | |||
[[User:Sfws|Sfws]] 00:34, 29 November 2012 (UTC) | * Created: [[User:Sfws|Sfws]] 00:34, 29 November 2012 (UTC) for legacy Cumulus | ||
* Amended: [[User:Sfws|Sfws]] ([[User talk:Sfws|talk]]) 19:49, 31 July 2021 (UTC) to also cover MX as at 3.12.0 | |||
