[CF-metadata] Proposal for new standard names - use of "sedimentation"

From: Tomoo Ogura <ogura>
Date: Wed, 9 Mar 2011 18:57:15 +0900

Dear Bert,

Many thanks for your comments and suggestions.

In the proposed new standard names, the word "sedimentation"
was meant to represent the gravitational settling of cloud
liquid water droplets.
I agree that the above usage of "sedimentation" does not
match a transition from one medium to another. Therefore,
we may need to look for another word to avoid confusion.

As an alternative, the suggested word "settling" sounds
good to me. In this case, the proposed standard names
will be as follows;

(a) tendency_of_mass_fraction_of_stratiform_cloud_liquid_water
    _in_air_due_to_settling_of_cloud_liquid_water,
and
(b) tendency_of_mass_fraction_of_stratiform_cloud_condensed_water
    _in_air_due_to_settling_of_cloud_liquid_water.

Best wishes,

Tomoo

----- Original Message -----
From: "Bert Jagers" <bert.jagers at deltares.nl>
To: "Tomoo Ogura" <ogura at nies.go.jp>; "Cameron-smith, Philip" <cameronsmith1 at llnl.gov>; "Jonathan
Gregory" <j.m.gregory at reading.ac.uk>
Cc: "Jennifer Kay" <jenkay at ucar.edu>; "Yoko Tsushima" <yoko.tsushima at metoffice.gov.uk>;
<cf-metadata at cgd.ucar.edu>
Sent: Wednesday, March 09, 2011 9:22 AM
Subject: Re: [CF-metadata] Proposal for new standard names - use of "sedimentation"


> Dear all,
>
> Unfortunately I have had far too little time to contribute to the CF mailing list over the past
> year, but I try to scan the titles of mails coming in and now and then I read a post. I didn't
> intend to read this thread until my eye accidentally caught the word "sedimentation" in body text.
> As someone involved in sediment transport in rivers, estuaries, coastal areas and to a much lesser
> oceans, I do have a strong association with the word "sedimentation". As a result I have some
> concerns with the appropriateness of the chosen word.
>
> If I interpret the most recent discussion correctly, the proposal is to use the word
> "sedimentation" for the slow downward motion of liquid water in the atmosphere; not being an
> atmospheric scientist I'm trying to grasp what that actually means. The discussion distinguishes
> it from definitions including terms like "accretion" and "autoconversion" which based on the
> description in the standard name table both seem to be related the growth of droplets and ice
> crystals; flocculation is the associated process in cohesive sediment modeling. Other processes
> that thus would be included in your new definition of "sedimentation" include: vertical advection
> due to general air velocity, turbulent mixing, relative gravitational settling of the
> droplets/crystals, ... more?
>
> In sediment transport, the words "sedimentation" and "deposition" are generally used to mean the
> reverse of "erosion". The former two mean that sediment falls from suspension onto the bed ("ocean
> floor"), whereas "erosion" means the uptake of sediment from the bed by the flow. Now, let us see
> how the word "sedimentation" was used before in CF names. The term "sedimentation" has so far been
> used in three standard names related to the ocean_mole_content of three chemical substances. These
> names are associated with 2D quantities (quantities per unit area) which matches my interpretation
> of the word (and the common use of this word): the amount of the substances considered (carbon,
> elemental nitrogen, and iron) in the ocean column is reduced due to the fact that organic
> suspended sediment settles onto the ocean floor. Basically it includes a transition from one
> medium (in the water column) to another medium (in/on the ocean floor). The newly proposed use of
> the term "sedimentation" does not match such a transition.
>
> Thinking along these lines I looked at the word "deposition" which is used more frequently in
> standard names. However, mostly it is used in combination with "dry", "wet" or "turbulent" and
> seem to be associated with the transition of substances from medium atmosphere to the medium ocean
> (or land): a 2D flux field of 2D variable "atmosphere mass content" in line with the use of the
> word "sedimentation" described above. The word "deposition" without "dry" or "wet" is less
> uniquely tied to a specific process. It has been used as the reverse of "sublimation" in
> tendency_of_mass_fraction_of_stratiform_cloud_ice_in_air_due_to_deposition_and_sublimation, as the
> sum of "dry deposition" and "wet deposition" (= "turbulent deposition" + "gravitational
> settling"), and in a non-specified manner in
> tendency_of_ocean_mole_content_of_iron_due_to_deposition_and_runoff_and_sediment_dissolution.
>
> In ocean modeling I would tend to use the word "settling" for the downward motion of sediment
> relative to the water without necessarily hitting the ocean floor, but also the word "settling"
> has so far only been used in combination with 2D variables of type "atmosphere mass content" and
> deposition.
>
> Best regards,
>
> Bert
> ------
>
Received on Wed Mar 09 2011 - 02:57:15 GMT