Following some feedback I will get back to the list later next week
with some clarifications.
Incidentally, the units should be siemens and not sieverts - thanks
to Steve Emmerson for spotting this. [As an ex-oceanographer I
was probably muddled by Sv for Sverdrups and have therefore used S for
electrical conductance in the past. But that's no excuse!]
Any further thoughts/comments welcome as this is the first time
I have been through this process.
Thanks,
Roger
________________________________________
From: Jonathan Gregory [j.m.gregory at reading.ac.uk]
Sent: 05 August 2016 14:55
To: Roger Brugge
Cc: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Atmospheric electrical measurements
Dear Roger
Thanks for your proposals and the useful background. I agree that these
quantities should have standard names. I have some suggestions:
> standard name electrical potential gradient
I suggest this should have "in_air" suffixed since CF stdnames apply to all
domains of geophysics. Also, it needs to indicate its sign. If it's positive,
does that mean the + is above and - below, or vice-versa? CF stdnames always
include an explicit sign convention when relevant. If you need both conventions
we can define two names. It should perhaps include "vertical" too but if the
sign convention implies it's vertical that wouldn't be needed.
> standard name vertical component of the conduction current density
Again, "in_air" and the sign convention are needed, and "electrical" as well,
but "component of the" can be omitted, as in many other component names e.g.
upward_heat_flux_in_air, eastward_sea_ice_velocity.
> standard name positive electrical conductivity
> standard name upward negative electrical conductivity
Again we need "in_air". These ones are scalars, I think, with no direction,
so I don't understand why the second one says "upward". They should have the
same form anyway. If I understand your description correctly, CF-like names
would be
electrical_conductivity_of_air_due_to_positive_ions
electrical_conductivity_of_air_due_to_negative_ions
Is that the right meaning?
You give variable names and long_names too, but CF doesn't standardise these.
Best wishes
Jonathan
On Fri, Aug 05, 2016 at 08:15:38AM +0000, Roger Brugge wrote:
> Date: Fri, 5 Aug 2016 08:15:38 +0000
> From: Roger Brugge <r.brugge at reading.ac.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> Subject: [CF-metadata] Atmospheric electrical measurements
>
> Some proposed new CF standard variable names for electrical properties of the atmosphere
>
> On behalf of the members of GLOCAEM (http://gtr.rcuk.ac.uk/projects?ref=NE/N013689/1) I would like to propose four new variables for the CF naming conventions, relating to the electrical properties of the atmosphere.
>
> Each of these can be measured/modelled at any height of the atmosphere but as they are often measured at near-ground level I have also included a ?close to the ground? version with the ending ?s? in each case.
>
> From: https://www.ngdc.noaa.gov/stp/space-weather/online-publications/miscellaneous/afrl_publications/handbook_1985/Chptr20.pdf
> Electric fields, currents, and conductivities as well positive and negative ions of greatly varying size and composition constitute the principal electrical properties of the atmosphere in fair weather. Air mass motions, pressure systems, winds, turbulence, temperature, and water vapour distributions have an important influence on the electrical properties in the troposphere through their control over the distributions of charged and uncharged aerosols and radioactive particles of terrestrial origin. These influences are greatest in the atmospheric exchange layer which is generally restricted to 2.5 km above the earth's surface. In the altitude region 30 to 90 km there is a transition from classical concepts of atmospheric electricity to the phenomena of ionospheric physics chiefly because of the changing atmospheric composition and increasing mean free path resulting in an increase in the concentration of free electrons. Recent studies have shown that the ionosphere, with its relatively high conductivity,
can no longer be regarded as the upper bound for atmospheric electrical processes. The exact nature of electrical coupling to the ionospheric and magnetospheric regions is currently under investigation.
>
> Good references for these quantities are D.R. McGorman and W.D. Rust, The Electrical Nature of Storms, Oxford University Press, Oxford, 1998 and E.P Krider et al The Earth?s Electrical Environment, Studies in Geophysics, National Academy Press, Washington, 1986 http://www.nap.edu/openbook.php?record_id=898&page=R1
> but the role and importance of each may be summarised as follows:
>
> 1. Electrical potential gradient. As a result of charge separation in disturbed weather regions and ionization sources in the atmosphere (including cosmic radiation) there exists a vertical electric potential gradient through the atmosphere. In fair weather conditions remote from pollution, this varies in a diurnal fashion (the so-called ?Carnegie curve?). In disturbed weather it becomes highly variable.
>
> 2. Vertical conduction current density. The potential gradient causes charged particles (ions) in the atmosphere to flow vertically. At the surface this is known as the air-Earth current.
>
> 3. positive (negative) electrical conductivity of the atmosphere. This is the polar (positive or negative) electrical conductivity resulting from positive (negative) small ions in atmospheric air. The conductivity is the product of the ion concentration and the ion mobility, and the elementary charge.
>
> Variable 1:
> long name vertical component of the atmospheric electrical potential gradient
> variable name pg (pgs when measured at station height close to the ground)
> standard name electrical potential gradient
> unit_name V/m
> note The potential gradient is considered positive in fair weather. (The vertical component of the electric field is negative in fair weather.)
>
> Variable 2:
> long name vertical conduction current density
> variable name jcz (jczss when measured at station height close to the ground)
> standard name vertical component of the conduction current density
> unit_name pA/m2
> note jczss is known as the air-Earth current at the surface
>
> Variable 3:
> long name positive electrical conductivity of the atmosphere
> variable name sigp (sigps when measured at station height close to the ground)
> standard name positive electrical conductivity
> unit_name fS/m
> note S denotes Sievert
>
> Variable 4
> long name negative electrical conductivity of the atmosphere
> variable name sign (signs when measured at station height close to the ground)
> standard name upward negative electrical conductivity
> unit_name fS/m
> note S denotes Sievert
>
> I'd be interested in any comments,
>
> Regards
> Roger Brugge
> University of Reading
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Received on Fri Aug 05 2016 - 10:09:57 BST
