I wonder what the units for "time" (=reftime+leadtime) would be, since
reftime is different for each trajectory?
Karl
On 5/17/11 1:24 PM, Benno Blumenthal wrote:
Aside from avoiding the use of the word "time" for anything that is
not "days since" or equivalent, I would do it as you described.
Instead of time I would use "leadtime" or "L", particularly so that I
could define "time" (reftime + leadtime) (with standard_name "time")
and include that as well in the variable list.
On Tue, May 17, 2011 at 3:02 PM, Karl Taylor <[email protected]
<mailto:[email protected]>> wrote:
Hi Benno,
This isn't really a comment on your email, but a question (only
somewhat related) occurred to me. When you store multiple
trajectories (or forecasts), each started from a difference
reference, but sampled in the same way (at equal intervals), how
should this be done? Suppose, for example, you want to store
ozone data from 10 freely moving balloons, with samples taken
hourly following release (for 24 hours), but each balloon released
at a different time. Would you do this as follows?
dimensions:
time = 24 ;
ref_time=10
variables:
float O3(time,ref_time) ;
O3:long_name = "mole_fraction_of_ozone_in_air" ;
O3:units = "1e-9" ;
O3:coordinates = "lon lat z" ;
double time(time)
time:standard_name = "elapsed_time??? or relative_time???"
time:long_name = "elapsed time since the beginning of the trajectory"
time:units = "hr"
double ref_time(ref_time) ;
ref_time:standard_name = "reference_time???" ;
ref_time:long_name = "time when balloon was released and the reference for
elapsed_time (relative_time)"
ref_time:units = "days since 1970-01-01 00:00:00" ;
float lon(time,ref_time) ;
lon:standard_name = "longitude" ;
lon:units = "degrees_east" ;
float lat(time,ref_time) ;
lat:standard_name = "latitude" ;
lat:units = "degrees_north" ;
float z(time,ref_time) ;
z:standard_name = "height_above_reference_ellipsoid" ;
z:units = "km" ;
z:positive = "up" ;
Note the possible standard_names (I think, suggested by others).
Best regards,
Karl
On 5/17/11 8:46 AM, Benno Blumenthal wrote:
CF has standard names forecast_reference_time, forecast_period and
time which are interrelated in a particular way.
I have a trajectory dataset which also has reference_time, period,
and time which are interrelated in the same way, but forecast is not
an appropriate descriptor: the reference_time is the start of the
trajectory, the period is the time relative to the start_time along
the trajectory.
I am wondering how important "forecast" is in the semantics of these
particular standard_names -- does it really have to be a forecast?
After all, these are the standard names for the time coordinates, e.g.
independent variables, while forecast is a property of the dependent
variables, i.e. how they were computed.
Do we need more general names? Am I taking the current names too literally?
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Dr. M. Benno Blumenthal [email protected]
<mailto:[email protected]>
International Research Institute for climate and society
The Earth Institute at Columbia University
Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
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