Re: questions about HDF4 SDS data

Hi Dennis,

Thank you very much. You really help me a lot. Have a good weekend!

Best,
Yi

On Fri, Jun 25, 2010 at 3:36 PM, Dennis Shea <shea@ucar.edu> wrote:

> Answers embedded below
>
>
>
> On 06/24/2010 02:16 PM, Yi Wang wrote:
>
>> Hi friends,
>> I want to plot the LW TOA Total-Sky field in
>> *CER_ZAVG_Aqua-FM4-MODIS_Edition2B_007005.200503.hdf* (you can find it
>> at
>>
>> ftp://ftp.hdfgroup.uiuc.edu/pub/outgoing/veer/MAP_DATA/files/CERES/CER_ZAVG_Aqua-FM4-MODIS_Edition2B_007005.200503.hdf
>> ).
>>
>> My codes is in *CER_ZAVG_Aqua-FM4-MODIS_Edition2B_007005.200503.ncl* (in
>> attachment).
>> But I have some questions.
>> *Question 1:*
>> There are four LW TOA Total-Sky fields in this hdf file:
>> 1.0 Degree Zonal -> Monthly Hourly Averages -> Observed TOA Fluxes -> LW
>> TOA Total-Sky
>> 1.0 Degree Zonal -> Monthly Averages -> Observed TOA Fluxes -> LW TOA
>> Total-Sky
>> Global -> Monthly Hourly Averages -> Observed TOA Fluxes -> LW TOA
>> Total-Sky
>> Global -> Monthly Averages -> Observed TOA Fluxes -> LW TOA Total-Sky
>> I found from
>> http://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclFormatSupport.shtmlthat
>> I probably can use
>> data = hdf_file->LW_TOA_Total_Sky__0 to specify 1.0 Degree Zonal ->
>> Monthly Hourly Averages -> Observed TOA Fluxes -> LW TOA Total-Sky,
>> and use data = hdf_file->LW_TOA_Total_Sky__1, data =
>> hdf_file->LW_TOA_Total_Sky__2, data = hdf_file->LW_TOA_Total_Sky__3 to
>> specify the other three LW_TOA_Total_Sky fields.
>> But, can I use something like
>> data =
>> hdf_file->LW_TOA_Total_Sky__Observed_TOA_Fluxes__Monthly_Hourly_Averages
>> __1_0_Degree_Zonal
>> to specify the LW TOA Total-Sky field? Because I just want to explicitly
>> show the full path.
>>
>
> ==
> No.
>
> The closest would be to explicitly show the named dimensions:
>
> data = LW_TOA_Total_Sky__0(LW_TOA_Total_Sky__0 ( Stats|:,
> Monthly_Hourly_Avgs|:, 1_0_deg_zonal_colat_zones|:,
> 1_0_deg_zonal_long_zones|: )
>
> Note: This is less efficient than
>
> data = LW_TOA_Total_Sky__0
> ===
>
> *Question 2:*
>>
>> There are several sentences in
>> http://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclFormatSupport.shtmlsaying
>> that "It also provides two additional attributes to the variable:
>> /hdf_group/, whose value is the HDF string name of the group, and
>> /hdf_group_id/, whose value is the same as the group number appended to
>> the end of the variable name."
>> Can I use something like printVarSummary() to print out the information
>> about hdf_group and hdf_group_id (Let us still take 1.0 Degree Zonal ->
>> Monthly Hourly Averages -> Observed TOA Fluxes -> LW TOA Total-Sky as an
>> example) ? If not, how can I get the hdf_group and hdf_group_id
>> information?
>>
>
> ==
> Do not know.
> ==
>
> *Question 3:*
>>
>> I used my codes to get a plot (see
>> *CER_ZAVG_Aqua-FM4-MODIS_Edition2B_007005.200503_LW_TOA_Total_Sky.pdf*
>> in the attachment). However, if I hope the range of X-axis (latitude) is
>> -89.5~89.5 (not 0~179), and the range of Y-axis is 0~7 (not 0.0~7.0).
>> How can I change the codes?
>> In addition, there is an overlap in the subtitles, how to avoid it (I
>> hope it can only shows "FIELD NAME: LW TOA Total-Sky" and "UNITS: Watt
>> per square meter" as the subtitles) ?
>>
>
> ==
> res@tmYLFormat = "f" ; no unnecessary zeros
>
> There are examples of modifying tick marks [tm] at
> http://www.ncl.ucar.edu/Applications/tickmarks.shtml
>
>
> ==
> lat = fspan(-89.5,89.5,180)
> lat!0 = "lat"
> lat@units = "degrees_north"
> data!1 = "lat"
> data&lat = lat
> ==
>
> When using gsn_csm*
>
> By default, the "units" attribute is plotted in the upper right.
> By default, the "long_name" is plotted in the upper left.
>
> If no long_name [or standard_name] then you can manually use (say)
>
> res@gsnLeftString = data@hdf_name ; hdf_name plotted in upper left
>
> See attached
>
> ==
> Please look at the mini-Graphics manual at:
>
> http://www.ncl.ucar.edu/Document/Manuals/
>
> ==
> Good luck
>
>
> Thanks a lot!
>> Best,
>> Yi
>>
>>
>>
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>
>
> --
> ======================================================
> Dennis J. Shea tel: 303-497-1361 |
> P.O. Box 3000 fax: 303-497-1333 |
> Climate Analysis Section |
> Climate & Global Dynamics Div. |
> National Center for Atmospheric Research |
> Boulder, CO 80307 |
> USA email: shea 'at' ucar.edu |
> ======================================================
>

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Received on Fri Jun 25 17:53:23 2010