Dear Mark
Thanks very much. Having the definitions detail the processes helps a lot.
I do have a remaining concern about terminology, though, which probably should
have been noticed earlier. In the guidelines, "condensed water" means liquid
or solid (ice), for instance in mass_fraction_of_cloud_condensed_water_in_air,
which says this explicitly in its definition.
For consistency, "condensation" should mean gas -> liquid or solid. The
A Met Soc glossary says "in general" that's what condensation means, but in
meteorology it means gas -> liquid.
http://glossary.ametsoc.org/wiki/Condensation
It's unfortunate that it's ambiguous! I think the general definition is more
satisfactory.
The same entry says "evaporation" means liquid or solid -> gas i.e. the reverse
of condensation. That is the sense in which we use it in some other standard
names e.g. water_evaporation_flux. However the AMS entry for evaporation gives
this as its first sense, but remarks that it's "usually" liquid->gas. Again, an
unsatisfactory ambiguity, and I would prefer the broader definition. With the
broader definitions, deposition (gas -> solid) is a subset of condensation,
and sublimation (solid -> gas) a subset of evaporation.
It looks like we may have some existing inconsistency between the meanings of
condensation and perhaps evaporation in standard names. Do you agree? If so we
should try to sort it out. An advantage of the broader definitions is you would
not have to say condensation_and_deposition, since it's all condensation.
Best wishes
Jonathan
----- Forwarded message from Mark Webb <mark.webb at metoffice.gov.uk> -----
> Date: Tue, 7 Jul 2015 15:45:06 +0100
> From: Mark Webb <mark.webb at metoffice.gov.uk>
> To: Jonathan Gregory <j.m.gregory at reading.ac.uk>
> CC: Mark Webb <mark.webb at metoffice.gov.uk>, cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] proposal for new standard names for some cloud
> quantities
> User-Agent: Mutt/1.5.20 (2009-12-10)
>
> Dear Jonathan,
>
> Thanks for your comments. I've updated the proposals in response to
> your comments below.
>
> > Thanks for these proposals, which look fine to me, except that it might be
> > helpful to describe the process in the definition of the due_to_ names, and:
> >
> > > Name:tendency_of_air_temperature_due_to_stratiform_cloud_and_precipitation
> > > Name:tendency_of_specific_humidity_due_to_stratiform_cloud_and_precipitation
>
> > what does "due to stratiform cloud" mean? - maybe "condensation" is missing?
>
> These terms include sources and sinks of humidity from a number or processes, of
> which condensation is just one. I didn't list the processes in the name
> since all reelvant processes should be included - this is to be
> consistent with existing standard names such as:
>
> tendency_of_air_temperature_due_to_stratiform_cloud_and_precipitation_and_boundary_layer_mixing
>
> Here is a modified version with hopefully clearer descriptions:
>
> Name:tendency_of_air_temperature_due_to_stratiform_cloud_and_precipitation
> Decription:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. Air temperature is the bulk temperature of the air, not the surface (skin) temperature. This variable should contain net latent heating effects of all processes which convert stratiform clouds and precipitation between water vapour, liquid or ice phases, including condensation (vapor to liquid), evaporation (liquid to vapor), freezing (liquid to ice), melting (ice to liquid), deposition (vapor to ice) and sublimation (ice to vapour).
> Units: K s-1
>
> Name:tendency_of_specific_humidity_due_to_stratiform_cloud_and_precipitation
> Description:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. "specific" means per unit mass. Specific humidity is the mass fraction of water vapor in (moist) air. This variable should contain the effects of all processes which convert stratiform clouds and precipitation to or from water vapor, including condensation (vapor to liquid), evaporation (liquid to vapor), deposition (vapor to ice) and sublimation (ice to vapour).
> Units: s-1
>
> > > Name:tendency_of_specific_humidity_due_to_convective_cloud_condensation_and_deposition
> > > Name:tendency_of_specific_humidity_due_to_stratiform_cloud_condensation_and_deposition
> > > Name:tendency_of_atmosphere_mass_content_of_water_vapor_due_to_convective_cloud_condensation_and_deposition
> > > Name:tendency_of_atmosphere_mass_content_of_water_vapor_due_to_stratiform_cloud_condensation_and_deposition
>
> > what is deposition (please excuse my ignorance of cloud physics)? - could it be
> > made more explicit?
>
> These terms specifically include condensation and deposition only (and should exclude other terms). I
> have made this cleared in the updated descriptions below.
>
> Name:tendency_of_specific_humidity_due_to_convective_cloud_condensation_and_deposition
> Description:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. "specific" means per unit mass. Specific humidity is the mass fraction of water vapor in (moist) air. This variable should contain only the processes of condensation (vapor to liquid) and deposition (vapor to ice) associated with the formation of convective clouds. Evaporation (liquid to vapor) and sublimation (ice to vapour) should not be included.
> Units: s-1
>
> Name:tendency_of_specific_humidity_due_to_stratiform_cloud_condensation_and_deposition
> Description:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. "specific" means per unit mass. Specific humidity is the mass fraction of water vapor in (moist) air. This variable should contain only the processes of condensation (vapor to liquid) and deposition (vapor to ice) associated with the formation of stratiform clouds. Evaporation (liquid to vapor) and sublimation (ice to vapour) should not be included.
> Units: s-1
>
> Name:tendency_of_atmosphere_mass_content_of_water_vapor_due_to_convective_cloud_condensation_and_deposition
> Description:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. "specific" means per unit mass. Specific humidity is the mass fraction of water vapor in (moist) air. This variable should contain only the processes of condensation (vapor to liquid) and deposition (vapor to ice) associated with the formation of convective clouds. Evaporation (liquid to vapor) and sublimation (ice to vapour) should not be included.
> Units: kg m-2 s-1
>
> Name:tendency_of_atmosphere_mass_content_of_water_vapor_due_to_stratiform_cloud_condensation_and_deposition
> Description:The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "tendency_of_X" means derivative of X with respect to time. "specific" means per unit mass. Specific humidity is the mass fraction of water vapor in (moist) air. This variable should contain only the processes of condensation (vapor to liquid) and deposition (vapor to ice) associated with the formation of stratiform clouds. Evaporation (liquid to vapor) and sublimation (ice to vapour) should not be included.
> Units:kg m-2 s-1
>
> Please let me know if I've misunderstood anything and/or if other changes are required.
>
> Thanks,
> Mark
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Mark Webb Climate Scientist
> Met Office Hadley Centre
> FitzRoy Road Exeter EX1 3PB United Kingdom
> Tel: +44 (0)1392 884515 Fax: +44 (0)1392 885681
> E-mail:mark.webb at metoffice.gov.uk http://www.metoffice.gov.uk
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
----- End forwarded message -----
Received on Wed Jul 08 2015 - 10:03:12 BST
