[ncl-talk] Reading isccp revisted
Dennis Shea
shea at ucar.edu
Fri Oct 13 08:23:18 MDT 2017
THX for the sample ISCCP hdf file. It looks pretty sparse!
IMHO: as the hdf file is constructed, it is USELESS!
%>ncl_filedump
Variable: f
Type: file
filename: ISCCP.D2.0.GLOBAL.2007.01.99.9999.GPC
path: ISCCP.D2.0.GLOBAL.2007.01.99.9999.GPC.hdf
file global attributes:
dimensions:
fakeDim0 = 6596
fakeDim1 = 130
[SNIP]
variables:
ubyte Data_Set_6 ( fakeDim0, fakeDim1 )
anno_label_1 : UTC 00
long_name : UTC 00
units : counts
format : I3
hdf_name : Data-Set-6
[SNIP]
Really, it looks like 'someone' had to do 'something' in hdf so they
created this useless file.
---
Because this is on a public forum, I am sure that an 'ISCCP' search will
contain this ncl-talk response. Hence, a disclaimer:
*I don't want to support ISCCP-D2 (or D1 or DX etc, etc, etc). Please send
all ISCCP questions to ISCCP people. *
The following deals with the *netCDF file(s) I created derived from the
original binary files*. Maybe, the following will be of use.
---
ISCCP ended 12/2009
--
https://climatedataguide.ucar.edu/ <=== excellent site to explore :-)
Search: ISCCP and click on ISCCP
Please read the "*Expert User Guidance*"
---
Click: *Get Data (External)*
One link, which lists all the variables, is here:
http://www.cgd.ucar.edu/cas/catalog/satellite/isccp/D2/means.html
The data set has been updated thru the end of the ISCCP project: 12/2009
ftp ftp.cgd.ucar.edu
anonymous
your_email
cd archive
ls
cd ISCCP
ls
get ncdump.isccp.1983-2009 <=== simple text file
get isccp.ps.gz <=== time series plots of ?all?
variables
get isccp.1983-2009.nc.gz <=== big file
quit
================ NCL D2 Stuff =================
NCL has been used on ISCCP binary data since 2004 (maybe earlier). As
noted, ISCCP hdf is useless.
The following is provided as deep background information. I have forgotten
everything I knew about the various scripts.
However, given NCL's backward compatibility, I speculate they would work.
*They read the original binary and not hdf files.*
---
d2bin2nc.ncl:
takes the binary and converts each year-month binary file to a
corresponding netCDF file. The script invokes a shared object that regrids
the data to a 2.5 degree grid. These were later placed onto a single file
via the netCDF operator: '*ncrcat*'
---
d2read_NCL.f:
I converted the original ISCCP provided D2-f77 code into a subroutine such
that a shared object (.so) could be created and invoked from an NCL script.
This uses ISCCP methodology for regridding to a 2.5 degree grid.
The original D2READ.f is at the "official" ISCCP software URL:
https://isccp.giss.nasa.gov/products/software.html
---
%>* WRAPIT* d2read_NCL.f
WRAPIT creates the shared object file: d2read_NCL.so
---
plot.ContourTimeS.ncl
Read the final netCDF file and creates time series plots for many
variables. I suggest you examine any ISCCP variables for discontinuities.
Remember ISCCP is a amalgamation of satellite inputs and these could change
over time.
Good luck
D
On Wed, Oct 11, 2017 at 5:13 AM, Marston Ward <marston.johnston at gu.se>
wrote:
> Hi,
>
>
>
> I’m trying to compare ISCCP products from COSP with real time data, i.e.,
> ISCCP D2 monthly means.
>
> I’ve never worked with ISCCP before, and, while I can download a lot of
> data from Earthdata, they are in formats I do not recognise nor know how to
> handle.
>
> Much of the isccp documents have email address that no longer work, so it
> is bit difficult to contact them.
>
>
>
> While doing a search on the NCL webpage revealed:
> https://www.ncl.ucar.edu/Applications/isccp.shtml
>
> But in this example the isccp data is already in netcdf format. I’m trying
> to get to this point.
>
>
>
> Further, in the NCL archives I came across a similar problem back in 2005:
> http://www.ncl.ucar.edu/Support/talk_archives/all/1699.html
>
> That seems to explain a bit how to read iSCCP D2 but much of this seem to
> me a black box.
>
>
>
> Given the above information, how can I find information on how to read the
> D2 data onto a regular lat lon grid using NCL?
>
> Anyone in the know, or with experience, out there and care to share?
>
>
>
> I’ve attached the SDS hdf file but I don’t know what’s in the file and the
> data looks very strange.
>
>
>
> Best,
>
> /M
>
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Marston S. Ward, PhD
>
> Department of Earth Sciences
>
> University of Gothenburg, Sweden
>
> Email: marston.johnston at gu.se
>
> SkypeID: marston.johnston
>
> Phone: +46-31-7864901 <+46%2031%20786%2049%2001>
>
> Only the fruitful thing is true!
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
> _______________________________________________
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>
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