Dear Thomas,
Thank you for your query. It is not necessary to open a trac ticket
because discussion of standard names normally takes place on the mailing
list.
I agree with Jonathan that the names themselves look fine, that
'displacement' is an appropriate term to describe the change in ice
position, and that it could be more widely applied in other standard
names should the need arise. The way you have constructed the names is
consistent with other sea_ice and sea_water velocity names.
Not all standard names proposals lead to a great deal of discussion. I
think that your names are fairly straightforward and certainly nobody
has objected to them. A very important part of including new names in
the table is to make sure the quantities are clearly defined. Please
see below for my suggested wording of the descriptions based on the
short definitions you have already provided. Please let me know if you
are happy with these or whether any clarifications are needed.
As the next update to the standard name table will take place on Tuesday
11th November and we have not yet finalised the definitions I would
prefer not to include the displacement names on this occasion. I try to
give a week's notice of planned changes to the table so that people can
check the list and hopefully catch any errors. This also allows me time
to do the editing of the table itself. Inevitably this means that on
occasion some names will just miss being included, but updates are done
every two months so there will not be a long delay before your names can
be added. If we can agree the definitions I can formally accept the
names, which means that they will definitely go into the table on
January 13th and in the meantime you will be free to start using them to
write your data. I hope that is an acceptable solution.
eastward_sea_ice_displacement [m]
'Displacement' means the change in geospatial position of an object that
has moved over time. The time interval during which the motion took
place must be specified using a bounds variable for the time coordinate
variable. A displacement is a vector quantity. Sea ice displacement is
defined as a two-dimensional vector, with no vertical component.
"Eastward" indicates a vector component which is positive when directed
eastward (negative westward). An eastward displacement is the distance
across the earth's surface calculated from the change in a moving
object's longitude during the interval given in the time bounds
variable.
northward_sea_ice_displacement [m]
'Displacement' means the change in geospatial position of an object that
has moved over time. The time interval during which the motion took
place must be specified using a bounds variable for the time coordinate
variable. A displacement is a vector quantity. Sea ice displacement is
defined as a two-dimensional vector, with no vertical component.
"Northward" indicates a vector component which is positive when directed
northward (negative southward). A northward displacement is the
distance across the earth's surface calculated from the change in a
moving object's latitude during the interval given in the time bounds
variable.
sea_ice_x_displacement [m]
'Displacement' means the change in geospatial position of an object that
has moved over time. The time interval during which the motion took
place must be specified using a bounds variable for the time coordinate
variable. A displacement is a vector quantity. Sea ice displacement is
defined as a two-dimensional vector, with no vertical component. "x"
indicates a vector component along the grid x-axis, when this is not
true longitude, positive with increasing x. An x displacement is
calculated from the difference in the moving object's grid x coordinate
between the start and end of the interval given in the time bounds
variable.
sea_ice_y_displacement [m]
'Displacement' means the change in geospatial position of an object that
has moved over time. The time interval during which the motion took
place must be specified using a bounds variable for the time coordinate
variable. A displacement is a vector quantity. Sea ice displacement is
defined as a two-dimensional vector, with no vertical component. "y"
indicates a vector component along the grid x-axis, when this is not
true longitude, positive with increasing y. A y displacement is
calculated from the difference in the moving object's grid y coordinate
between the start and end of the interval given in the time bounds
variable.
sea_ice_displacement
'Displacement' means the change in geospatial position of an object that
has moved over time. The time interval during which the motion took
place must be specified using a bounds variable for the time coordinate
variable. The displacement is the distance across the earth's surface
calculated from the change in a moving object's (lon,lat) position
between the start and end of the interval given in the time bounds
variable. A displacement is a vector quantity. Sea ice displacement is
defined as a two-dimensional vector, with no vertical component.
direction_of_sea_ice_displacement [degrees]
"direction_of_X" means direction of a vector, a bearing. A displacement
is a vector quantity. Sea ice displacement is defined as a
two-dimensional vector, with no vertical component. 'Displacement'
means the change in geospatial position of an object that has moved over
time. The time interval during which the motion took place must be
specified using a bounds variable for the time coordinate variable. The
displacement is the distance across the earth's surface calculated from
the change in a moving object's (lon,lat) position between the start and
end of the interval given in the time bounds variable. The 'direction
of displacement' is the angle between due north and the displacement
vector.
Best wishes,
Alison
>
> Dear Alison,
>
> Although there has been very little discussion on the topic, I had
come
> with some new standard names
> for the satellite ice-drift product I am issuing. Those were not asked
> for in the trac but in the
> mailing list (first mail sent on 24/10/2008). Those are:
>
> > eastward_sea_ice_displacement [m] (length of [lon0,lon1] on
> Earth surface)
> > northward_sea_ice_displacement [m] (length of [lat0,lat1] on
> Earth surface)
> > sea_ice_x_displacement [m] (length from P0 to P1, taken
> along the grid's X axis)
> > sea_ice_y_displacement [m] (length from P0 to P1, taken
> along the grid's Y axis)
> > sea_ice_displacement [m] (the length [P0,P1] on Earth
> surface)
> > direction_of_sea_ice_displacement [degrees] (the direction to North
> of the [P0,P1] vector)
>
> They are built on the 'sea_ice_velocity' model, which is already in
the
> table of standard names.
>
> Answer from Jonathan was (same day):
> > These all look good to me. I agree that "displacement" conveys the
> idea of
> > moving from A to B. A displacement would be extensive in time, and
> the time
> > bounds would record the two measurement instants between which the
> displacement
> > occurred. By contrast, a velocity is intensive in time.
>
> And I am afraid nobody reacted or built upon this thread. Is it still
> too early to include those
> names? Should I insert a proper entry in the trac system? Do you need
a
> better wordy description for
> those variables?
>
> Just let me know.
>
> Cheers,
> Thomas
>
==> Please note new email address: alison.pamment at stfc.ac.uk <==
------
J Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
Rutherford Appleton Laboratory Email: alison.pamment at stfc.ac.uk
Chilton, Didcot, OX11 0QX, U.K.
--
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Received on Wed Nov 05 2008 - 08:37:38 GMT
