[IDV #GYA-404192]: aggregatin nc files

Hi HP-

> Thanks for the quick reply. This ncML things is quite nice, though you
> have get used to it.I have created the ncML file from your template.
> However, there are problems that do not manifest themselves the same way
> under XP and 64-bit Linux. I report what happens under Linux.

Maybe I should test my solutions before I send them out. ;-)

> When I take you template character by character the last image of the
> sequence is displayed (under XP things stop already before I can move on
> to the Field Selector) and I get the following message:
> 
> 06-Aug-2008 10:21:14 ucar.nc2.ncml.AggregationNew buildDataset
> SEVERE: file:/home/user/Desktop/20080720-31_ma_GOME2_NO2Column/NO2.ncml 
> aggNewDimension cant find variable N02
> Unknown unit [10^15_molec_cm-2]
> (...)
> 
> I then discovered that you put
> <variableAgg name="N02"/>
> where N02 is supposed to be NO2 (nitrous dioxide). 

I must have been brain dead when I responded.   I knew it is NO2, but my
fingers typed N02.

>Correcting for this and trying to open the ncML file again open a window 
>titled No Gridded Data and asks whether I want to it as load another data type.
> 
> Looking into the ncML website I could not find a clue on what's going wrong.

Well, the docs turned out to be a little misleading.  The default type for
a variable is String, to time ends up being string variable.  But for
times as strings, they need to be in the ISO standard.

So, if you change:

<variable name="time">

to:

<variable name="time" type="int">

it should work.  John is going to fix the web page as well.

> (BTW "unknown unit" unknown to whom and what could be the consequences?)

Unknown to the units package.  I don't think you could get away with a
unit spec of 10^15_molec_cm-2 in a journal publication.  What's a molec
anyway? For ISO units, it would be something like "1.66E-9 mole cm-2" since 1 
mole
it ~6.02E23 molecules (if that's what a molec is).  The consequence it that
you wouldn't be able to use the Change Unit menu since the unit would
end up being null.

You could use NcML to clean up the units as well.  You could add in:

<variable name="NO2">
<attribute name="units" value="1.66E-9 mole cm-2"/>
</variable>

after the time variable block (or after the aggregation block).

Let me know if you still have problems with this method.

Don
> 
> Unidata IDV Support wrote:
> > Hi HP-
> >
> >
> >> Full Name: HansPeter Roesli
> >> Email Address: address@hidden
> >> Organization: EUMETSAT
> >> Package Version: 2.6a3 build date:@DATE@
> >> Operating System: Linux
> >> Hardware: Java: home: /home/user/IDV_2.6a3/jre version: 1.6.0_07 j3d:1.5.2 
> >> fcs (build4)
> >> Description of problem: HI
> >>
> >> I tried to aggregate a sequence of daily nc files showing global NO2 
> >> columns from GOME-2 on
> >> Metop 
> >> (http://wdc.dlr.de/data_products/SERVICES/GOME2NRT/archive.php?spec=NO2).
> >> However, it does not work and ends this state. I also attach a sample file.
> >>
> >
> > These files have no time in them.  Were you trying to use the
> > "Make a time sequence from single time grids/images" formula to aggregate 
> > these?
> > You could create an NcML file to do the aggregation manually.  You can
> > see some examples at:
> >
> > http://www.unidata.ucar.edu/software/netcdf/ncml/v2.2/Aggregation.html
> >
> > under the JoinNew section.  You would create a new time dimension like:
> >
> > <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
> >
> >    <variable name="time">
> >      <attribute name="units" value="days since 2008-07-22 00:00"/>
> >      <attribute name="_CoordinateAxisType" value="Time" />
> >      <values>0 1 2</values>
> >    </variable>
> >
> >    <aggregation dimName="time" type="joinNew">
> >     <variableAgg name="N02"/>
> >     <netcdf 
> > location="file:/home/user/Desktop/20080720-31_ma_GOME2_NO2Column/GOME2.L3.NO2.VCD.NRT.GDP-4.20080722.nc"
> >  />
> >     <netcdf 
> > location="file:/home/user/Desktop/20080720-31_ma_GOME2_NO2Column/GOME2.L3.NO2.VCD.NRT.GDP-4.20080723.nc"
> >  />
> >     <netcdf 
> > location="file:/home/user/Desktop/20080720-31_ma_GOME2_NO2Column/GOME2.L3.NO2.VCD.NRT.GDP-4.20080724.nc"
> >  />
> >    </aggregation>
> >
> > </netcdf>
> >
> >
> >> BTW marcos
> >> field short and
> >> long name both deliver the same string (NO2). That's porbably due to the 
> >> coding by the provider, isn't it?
> >>
> >
> > For netCDF files, we use the "long_name" attribute to get a descriptive 
> > name.
> > However, these files look like:
> >
> >    float NO2(latitude=720, longitude=1440);
> >      :NO2 = "NO2_Total_Column";
> >      :units = "[10^15_molec_cm-2]";
> >      :value = "Retrieval for given date";
> >      :date = "20080722";
> >      :version = "GDP-4.2";
> >
> > if the :N02 attribute was  :long_name, then we'd pick it up.
> >
> > Also, none of the units are valid specifications.
> >
> > Don
> >
> >
> >> Creating display: Color-Shaded Plan View
> >> org.python.core.PyException
> >>
> >> ******************
> >> Stack trace:
> >> Traceback (innermost last):
> >> File "<string>", line 1, in ?
> >> File "<string>", line 230, in makeTimeSequence
> >> at visad.Set.<init>(Set.java:148)
> >> at visad.SimpleSet.<init>(SimpleSet.java:58)
> >> at visad.SampledSet.<init>(SampledSet.java:47)
> >> at visad.GriddedSet.<init>(GriddedSet.java:72)
> >> at visad.Gridded1DSet.<init>(Gridded1DSet.java:130)
> >> at visad.Gridded1DDoubleSet.<init>(Gridded1DDoubleSet.java:107)
> >> at visad.Gridded1DDoubleSet.create(Gridded1DDoubleSet.java:174)
> >> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> >> at 
> >> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> >> at 
> >> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> >> at java.lang.reflect.Method.invoke(Method.java:597)
> >>
> >> visad.UnitException: visad.UnitException: Set: units dimension 1 does not 
> >> match Domain dimension 2
> >>
> >>
> >>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: GYA-404192
> > Department: Support IDV
> > Priority: Normal
> > Status: Open
> >
> >
> >
> 
> 


Ticket Details
===================
Ticket ID: GYA-404192
Department: Support IDV
Priority: Normal
Status: Open