[ncl-talk] CNL read CALIPSO v4.51 data

[Dave Allured - NOAA Affiliate]

HDF4, that is a good clue.  The dump utility for HDF4 is "hdp".  Do you
have it?   There are many options.  To start, try "hdp -H list" and go from
there.
https://support.hdfgroup.org/hdf4/

Note that HDF4 tools include an HDF4 to HDF5 converter, which they
recommend.

NCL addfile might be identifying this file as HDF-EOS, which is based on
HDF4.  See addfile documentation.  Try switching the filename extension
from .hdf to .he4 and see if that improves NCL readability.


On Thu, Sep 4, 2025 at 3:39 PM Rick Brownrigg <brownrig at ucar.edu> wrote:

> h5dump can't open it.  Running "strings" on that filename indicates its an
> HDF4.2 file?
>
>
> On Thu, Sep 4, 2025 at 3:30 PM Dave Allured - NOAA Affiliate via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> More diagnostics needed.  Someone please show output from:
>>
>> NCL:
>> fh = addfile("CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-
>> 00-11ZD.hdf","r")
>> print (fh)
>>
>> Linux:
>> h5dump -BH CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf
>>
>>
>> On Thu, Sep 4, 2025 at 3:23 PM Rick Brownrigg via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Hi,
>>>
>>> As that file resides on /glade, I was able to access it and duplicate
>>> the problem. I can print() that variable, but I can't load it into an NCL
>>> variable. Its rather large -- 699MB. Perhaps that's the problem?
>>> Interestingly, if I run "ncdump" on that file, I get:
>>>
>>>  ncdump
>>> /glade/derecho/scratch/zhifengy/data/experiment_input/doe_cloud_africa/CALIPSO/CAL_LID_L2_VFM-Standard-V4-51/test/CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf
>>>
>>> ncdump:
>>> /glade/derecho/scratch/zhifengy/data/experiment_input/doe_cloud_africa/CALIPSO/CAL_LID_L2_VFM-Standard-V4-51/test/CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf:
>>> NetCDF: Attempt to use feature that was not turned on when netCDF was built.
>>>
>>> Rick
>>>
>>>
>>> On Thu, Sep 4, 2025 at 3:16 PM Ehsan Taghizadeh via ncl-talk <
>>> ncl-talk at mailman.ucar.edu> wrote:
>>>
>>>> Hi Zhifeng,
>>>>
>>>> Could you please add the following commands before your addfile
>>>> command:
>>>>
>>>> exists =
>>>> isfilepresent("CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf")
>>>> print (exists)
>>>>
>>>> I wonder if your ncl script and the file are in the same place.
>>>> In case it returns True, could you please add the following commands
>>>> just after reading your file (after addfile command):
>>>>
>>>> names = getfilevarnames(
>>>> "CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf")
>>>> print (names)
>>>>
>>>>
>>>> *-----------------------------------------------------------------------------*
>>>> *Best regards,*
>>>> *Ehsan Taghizadeh*
>>>>
>>>> On Thursday, September 4, 2025 at 01:37:05 PM PDT, Zhifeng Yang via
>>>> ncl-talk <ncl-talk at mailman.ucar.edu> wrote:
>>>> Hi all,
>>>>
>>>> I am using NCL 6.6.2 to read CALIPSO latitude, longitude, and
>>>> Feature_Classification_Flags variable from CAL_LID_L2_VFM-Standard-V4-51.
>>>>
>>>>   fh =
>>>> addfile("CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf","r")
>>>>    lath      = fh->Latitude(:, 0)
>>>>    lonh      = fh->Longitude(:, 0)
>>>>    vfmh      = fh->Feature_Classification_Flags
>>>>
>>>> However, I got the error below
>>>> fatal:HDF: An error occurred while attempting to read variable
>>>> (Feature_Classification_Flags) from file
>>>> (/glade/derecho/scratch/zhifengy/data/experiment_input/doe_cloud_africa/CALIPSO/CAL_LID_L2_VFM-Standard-V4-51/test/CAL_LID_L2_VFM-Standard-V4-51.2017-08-21T14-00-11ZD.hdf)
>>>>
>>>> Do you have any idea about this? Thanks,
>>>>
>>>> Best,
>>>> Zhifeng
>>>>
>>>
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