Standard names: urban_thermal_climate_index, physiological_equivalent_temperature and perceived_temperature

[VossV]

Proposer's name AtMoDat Project - Vivien Voss Date 2022-05-17.

- Term universal_thermal_climate_index - Description Universal Thermal Climate Index (UTCI) is an equivalent temperature of the actual thermal condition. It is the air temperature of a reference condition causing the same dynamic physiological response in a human body considering its energy budget, physiology and clothing adaptation [utci.org]. - Units Degree_C

- Term physiological_equivalent_temperature - Description Physical equivalent temperature (PET) is an equivalent air temperature of the acutal thermal condition. It is the air temperature of a reference condition without wind and solar radiation at which the heat budget of the human body is balanced with the same core and skin temperature. - Units Degree_C

- Term perceived_temperature - Description Perceived temperature (PT) is an equivalent air temperature of the actual thermal condition. It is the air temperature of a reference condition causing the same thermal perception in a human body considering air temperature, windspeed, humidity, solar and thermal radiation as well as clothing and activity level. - Units Degree_C

Relevance: UTCI, PET and PT are established in human-biometeorology, but there are no CF standard names to write out model output in a standardised manner.

Some references for the defintion of the proposed standard_names can be found here: UTCI: utci.org PET: Höppe (1999): The physiological equivalent temperature – a universal index for the biometeorological assessment of the thermal environment, https://doi.org/10.1007/s004840050118 PT: Staiger et al. 2012: The perceived temperature – a versatile index for the assessment of the human thermal environment. Part A: scientific basics, https://doi.org/10.1007/s00484-011-0409-6.

[JonathanGregory]

Dear Vivien @VossV

Thanks for your proposals. Is your proposed perceived_temperature the same as the quantity with the existing standard name of apparent_temperature, which in its definition says it's the "perceived temperature"?

The UTCI isn't as self-explanatory as the other two. It's a temperature as well, whereas "index" sounds like something dimensionless. Despite the word "climate", the definition doesn't apparently relate to climate, but to the prevailing conditions, like the other two. What's the difference between physiological equivalent temperature and UTCI?

Best wishes

Jonathan

[VossV]

Dear Jonathan,

Thank you for your feedback! Indeed, the terms are similar. Several variables have been defined that represent thermal comfort in the environment.

Perceived_temperature and apparent_temperature are not the same. Apparent_temperature refers to one of three different variables, depending on the air temperature. In hot conditions apparent_temperature refers to head_index_of_air_temperature, which considers air temperature and humidity. Perceived_temperature is based on air temperature, humidity, wind and radiation. It is calculated based on the human energy budget considering also activity and adaptation of clothing.

UTCI and PET are both reference temperatures, but they are calculated using different models and reference conditions to calculate the human energy budget. UTCI refers to light activity (walking) and allows for clothing adaptation, while PET does not consider clothing and refers to a low activity level (office work).

Some aspects of the name UTCI may seem counter intuitive. However, this name was coined by the International Society of Biometeorology Commission [1] and has been in use for over a decade [2], sometimes as Universal Thermal Comfort Index. For the use of the term index with a temperature unit, we refer to heat_index_of_air_temperature, which also has the standard name index but with temperature units. (However, we would argue that _of_temperature is not a suitable addition for the proposed variables, since they do not describe a property of the air temperature, but the full thermal conditions.)

Please let us know if we should clarify this further. An overview of biometeorological variables can also be found in [3]. The three proposed variables are part of official guidelines in Germany, described by VDI Guideline 3787 Blatt 2 [4].

Kind regards, Vivien

[1] https://link.springer.com/article/10.1007/s00484-012-0546-6 [2] https://link.springer.com/content/pdf/10.1007%2Fs00484-021-02174-1.pdf [3] https://link.springer.com/article/10.1007/s00484-018-1591-6 [4] https://www.vdi.de/richtlinien/details/vdi-3787-blatt-2-umweltmeteorologie-methoden-zur-human-biometeorologischen-bewertung-der-thermischen-komponente-des-klimas-1

[larsbarring]

Hi, A couple of thoughts: 1: I was initially slightly confused by the title "...urban thermal comfort index..." and the definition. But in your response I found the explanation. I agree that UTCI as in Universal Thermal Climate Index is well established, but I did not know (at least well enough) about the alternative interpretation of the acronym (Urban Thermal Comfort Index) -- they are in fact the same, right? If so it might be useful to mention this in the explanation. Something like:

• Term universal_thermal_climate_index
• Description Universal Thermal Climate Index (UTCI) is an equivalent temperature of the actual thermal condition. It is the air temperature of a reference condition causing the same dynamic physiological response in a human body considering its energy budget, physiology and clothing adaptation [utci.org]. Sometimes this index is also known as "Urban Thermal Comfort Index".
• Units Degree_C

While the established unit for UTCI is degree_C we usually use the canonical unit in the standard name table, but then you are of course free to use any convertible unit (as degree_C). I am not sure which is mot appropriate here; keep canonical units or accept the established unit (@JonathanGregory: any thoughts?)

2: Regarding physiological_equivalent_temperature I understand that "PET" is a well-known acronym within the biometeorological community, but with respect to CF there is another well-established community where "PET" is *potential evapo[transpi]ration". I wonder whether it might be better not to include the acronym "PET" here, what do you think?

[JonathanGregory]

Dear Vivien

If perceived_temperature and apparent_temperature are not the same, then it's fine to have both in the standard name table. However, in that case, the definition of apparent temperature should be modified to say that it is not (the same as) perceived temperature, instead of saying that it is perceived air temperature! :-) It would also be helpful to say in the definition of perceived_temperature that it's not the same as apparent_temperature.

If UTCI can also stand for "urban thermal comfort index", I would find that phrase preferable, since UTCI isn't a universal notion, and doesn't relate to climate. We often use different terms in standard names from the ones commonly used in practice, when the common ones are potentially confusing or unclear to non-experts. Alternatively, if it's ambiguous what it stands for, maybe we could use the acronym itself. We don't include many abbreviations in standard names, but there are some precedents for including some non-self-explanatory word if the concept is well-defined by practice but can't be explained in few words. Maybe we could call it utci_temperature?

Lars is right that it's usual to put K as the canonical unit for temperature, but there are a handful with degree_C already.

Best wishes

Jonathan

[VossV]

Dear Lars, dear Jonathan

thank you for your feedback! and sorry for the late response.

We agree that universal_thermal_comfort_index seems a good compromise.

We propose to use the standard name 'physiological_equivalent_temperature' and to mention the abbreviation PET only in the term description. We think this should avoid any confusion as the difference of the two unrelated variables is clear.

Kind regards, Vivien

[JonathanGregory]

Dear Vivien

We agree that universal_thermal_comfort_index seems a good compromise.

Would it be OK to call it universal_thermal_comfort_index_temperature, because it is a temperature. An "index" sounds like an arbitrary dimensionless quantity.

We propose to use the standard name 'physiological_equivalent_temperature' and to mention the abbreviation PET only in the term description. We think this should avoid any confusion as the difference of the two unrelated variables is clear.

That seems sensible. You could even remark in the definition that "PET" should not be confused with potential evapotranspiration.

Cheers

Jonathan

[VossV]

Dear Jonathan,

thank you for your suggestions.

UTCI being an index with unit K indeed seems counter-intuitive. However, we believe this is more consistent for two reasons. There are some precedents in the current list of standard names where an index variable is associated with a unit, e.g. atmosphere_stability_k_index, lightning_potential_index and others. In this context it would seem more consistent to remain with UTCI as universal_thermal_comfort_index. This is also the established terminology in the field.

We have added the suggested note to the definition of PET.

Kind regards, Vivien

Updated Version:

Term: universal_thermal_comfort_index

• Description: Universal Thermal Comfort Index (UTCI) is an equivalent temperature of the actual thermal condition. It is the air temperature of a reference condition causing the same dynamic physiological response in a human body considering its energy budget, physiology and clothing adaptation [utci.org].
• Units: Degree_C

Term: physiological_equivalent_temperature

• Description: Physiological equivalent temperature (PET) is an equivalent air temperature of the acutal thermal condition. It is the air temperature of a reference condition without wind and solar radiation at which the heat budget of the human body is balanced with the same core and skin temperature. Note that PET here is not potential evapotranspiration.
• Units: Degree_C

Term: perceived_temperature

• Description: Perceived temperature (PT) is an equivalent air temperature of the actual thermal condition. It is the air temperature of a reference condition causing the same thermal perception in a human body considering air temperature, windspeed, humidity, solar and thermal radiation as well as clothing and activity level. It is not the perceived air temperature, that either derives from wind chill and heat index, which has the standard_name apparent_air_temperature.
• Units: Degree_C

[JonathanGregory]

Dear Vivien

OK, that's fine. Thanks! I assume Alison @japamment will consider this proposal for the standard name table soon.

Best wishes

Jonathan

[feggleton]

Thanks for your proposal and to @JonathanGregory I think you have covered all the considerations here. I don't think including the note on potential evapotranspiration is really necessary here but others may think otherwise which is perfectly fine. @japamment could you have a look at these terms to confirm before acceptance. Thanks all

[github-actions[bot]]

This issue has had no activity in the last 30 days. This is a reminder to please comment on standard name requests to assist with agreement and acceptance. Standard name moderators are also reminded to review @feggleton @japamment

[JonathanGregory]

I see physiological_equivalent_temperature and perceived_temperature in version 81, but not universal_thermal_comfort_index. Do you know what's happened to this, @feggleton @japamment?

[feggleton]

@JonathanGregory Thanks for flagging. I see what has happened here. The table contains this term:

universal_thermal_climate_index

Universal Thermal Comfort Index (UTCI) is an equivalent temperature of the actual thermal condition. Reference: utci.org. It is the air temperature of a reference condition causing the same dynamic physiological response in a human body considering its energy budget, physiology and clothing adaptation.

The term name is wrong and should be universal_thermal_comfort_index. I will put an alias in to correct this for the next update. Apologies for this.

[feggleton]

Added to the editor: https://cfeditor.ceda.ac.uk/proposals/1

[JonathanGregory]

I see. Thanks, Fran @feggleton.

[japamment]

Closing this issue as the names were published in V81 of the standard name table.

[japamment]

This issue is already closed but I am recording that the alias universal_thermal_climate_index -> universal_thermal_comfort_index was published in V82 of the standard name table.