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

[Rick Brownrigg]

Thanks for that tip about hdp, Dave.  Using NCL to
print(f->Feature_Classification_Flags) indicates it has dimensions

Dimensions and sizes: [fakeDim18 | 63360] x [fakeDim19 | 5515]

But hdp shows:

Variable Name = Feature_Classification_Flags
Index = 9
Type= 16-bit unsigned integer
Ref. = 11
Compression method = NONE
Rank = 2
Number of attributes = 3
Dim0: Name=fakeDim18
Size = UNLIMITED (currently 4224)
Scale Type = number-type not set
Number of attributes = 0
Dim1: Name=fakeDim19
Size = 5515
Scale Type = number-type not set
Number of attributes = 0

So if I have NCL read the variables as:

  foo = f->Feature_Classification_Flags(:4223, :)

It seems to load fine.  If I say

  foo = f->Feature_Classification_Flags(:4224, :)

it errs out.  The same is true of some of the other variables, ex.
Latitude's 1st dimension is only 4224, not 63360.

Rick



On Thu, Sep 4, 2025 at 4:06 PM Dave Allured - NOAA Affiliate via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Where is the documentation for CALIPSO files?
>
>
> On Thu, Sep 4, 2025 at 4:03 PM Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> 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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