Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Hi John, Rich, all, Thanks for this. Just thought of another question - is it possible to find out what the min-max range of "natural" coordinates is, or would I have to perform the transformation (theoretically for every timestep) and search the returned 3D array? I suppose that I could do the transformation for one timestep only and assume the range won't be very different for other timesteps since the free surface (or surface pressure) isn't likely to vary too much? Rich - yes, I probably could use the IDV routines although that means another dependency for the sake of one routine, plus I need to look at how to instantiate the IDV objects correctly in all cases. Just requires a bit more thought. Cheers, Jon From: netcdf-java-bounces@xxxxxxxxxxxxxxxx [mailto:netcdf-java-bounces@xxxxxxxxxxxxxxxx] On Behalf Of John Caron Sent: 04 May 2011 17:47 To: netcdf-java@xxxxxxxxxxxxxxxx Subject: Re: [netcdf-java] Questions about handling dimensionless coordinates On 5/4/2011 9:51 AM, Jon Blower wrote: Hi, I'd like to add support for dimensionless vertical coordinates in ncWMS and I have a few questions: How common is it for the transformation between dimensionless coords and natural coords to be time-dependent? Under what circumstances would this occur? Does it happen when the coordinate depends on a pressure field that varies with time? yes, thats the common case that ive seen: surface_pressure(time) for hybrid/sigma coordinates. Im not sure about the ocean vertical coordinates. If the VerticalTransform exists, can I assume that getCoordinateArray() will always return a valid array, i.e. that nj4 has automatically found all the auxiliary fields necessary to create the transform (such as pressure)? yes, it will fail fast (at construction) if theres a problem. I can see how to get the units of the transformed vertical coordinate (i.e. the "natural" coords, via VerticalTransform.getUnitString()) but how can I get the "positive" direction? In other words, if the natural coordinates are in metres, how do I know whether this is depth or height? hmm, i never thought of that problem. im guessing a domain expert could look at these: http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#dimensionless-v-coord and tell us the right answer, which we could then embed into the code. What would be the most "natural" interpolation method in the vertical when transforming a gridded field from dimensionless coordinates into levels - nearest-neighbour or linear? (Or something else?) dunno - id guess linear or log, depending on the transform. perhaps the domain expert could look at the above list and give some advice. Thanks, Jon -- Dr Jon Blower Technical Director, Reading e-Science Centre Environmental Systems Science Centre University of Reading, UK Tel: +44 (0)118 378 5213 http://www.resc.reading.ac.uk<http://www.resc.reading.ac.uk/> _______________________________________________ netcdf-java mailing list netcdf-java@xxxxxxxxxxxxxxxx<mailto:netcdf-java@xxxxxxxxxxxxxxxx> For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
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