Difference between revisions of "GEOS-5 issues"

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(New page: == Wet scavenging in GEOS-5 == === 09-Jan-2008 === There can be significant differences in the amount of tracer lost to wet scavenging in GEOS-5 as compared to the equivalent run in GEOS...)
 
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== Wrong unit tag for RH in GEOS-5 raw data files ==
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The GEOS-5 raw met data files (both in versions 5.0.1 and 5.1.0) at 0.5 x 0.667 resolution have the wrong unit tag for the 3-D relative humidity field.  The field is given as a fraction but the unit tag in the HDF file says percent. 
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The quick fix is to just multiply RH * 100 as soon as it is read from disk in a6_read_mod.f.
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'''''Bob Yantosca (yantosca@seas.harvard.edu) wrote:'''''
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:Hi Rob,
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:I think I may have found a slight bug in one of the GEOS-5 fields.  The Relative Humidity variable in the tavg3d_dyn_v files seems to have the wrong unit tag.  The RH data is unitless but the data tag says percent.
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:I looked at the file:
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    DAS.ops.asm.tavg3d_dyn_v.GEOS510.20080320_0000.V01.hdf
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:and I was able to read it into IDL with HDF_BROWSER, which gives info about each data block:
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    ** Structure <108eeeb8>, 15 tags, length=152, data length=136, refs=2:
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      ...
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      LABEL          STRING    'Relative humidity'
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      NAME            STRING    'RH'
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      ...
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      TYPE            STRING    'FLOAT'
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      UNIT            STRING    'percent'
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:But then if you print out the min and max of the data I got:
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    Time      Time from          Date          Time
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    Index    1993 (s)      (YYYYMMDD)      (HHMMSS)
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    ===============================================================================
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        1  480124806.0        20080320        000000
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    ### RH min, max:  0.0000000E+00  1.113281 
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:If it were % it would be 111.3281%.  So there is a factor of 100 difference.  Can you confirm this?
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:I believe that RH is unitless for both the 5.0.1 and the 5.1.0 data.  I checked a couple of data files that I had created from both data sets:
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      date    time  field    min        max 
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    20050101 180000 RH    0.000001  1.052381  --> 2x25 file regridded from GEOS-5.0.1 data
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    20080101 180000 RH    0.000000  1.055233  --> 2x25 file regridded from GEOS-5.1.0 data
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:Also, the last version of the [http://gmao.gsfc.nasa.gov/operations/GEOS5_V1_File_Specification.pdf GEOS-5 file spec)] that I have says RH is %.
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:For the time being I'll put a line of code into GEOS-Chem to multiply RH by 100 (our algorithm expects RH in %).  That is the easiest fix.
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:Thanks much,
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:Bob Y.
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'''''Rob Lucchesi (rlucchesi@gmao.gsfc.nasa.gov) replied:'''''
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:Bob,
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:You are right.  RH as written by the model is a fraction, not a percentage.  We will have to modify the documentation and metadata in future products to reflect this.  Note that the RH derived from the analysis (in the inst3d_met_p product) is a percentage.  RH in the MERRA products is also fractional, but the documentation reflects that.
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:Thanks for the info.
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:Rob Lucchesi
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:GMAO
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--[[User:Bmy|Bmy]] 10:11, 1 April 2008 (EDT)
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== Wet scavenging in GEOS-5 ==
 
== Wet scavenging in GEOS-5 ==
  

Revision as of 14:11, 1 April 2008

Wrong unit tag for RH in GEOS-5 raw data files

The GEOS-5 raw met data files (both in versions 5.0.1 and 5.1.0) at 0.5 x 0.667 resolution have the wrong unit tag for the 3-D relative humidity field. The field is given as a fraction but the unit tag in the HDF file says percent.

The quick fix is to just multiply RH * 100 as soon as it is read from disk in a6_read_mod.f.

Bob Yantosca (yantosca@seas.harvard.edu) wrote:

Hi Rob,
I think I may have found a slight bug in one of the GEOS-5 fields. The Relative Humidity variable in the tavg3d_dyn_v files seems to have the wrong unit tag. The RH data is unitless but the data tag says percent.
I looked at the file:
   DAS.ops.asm.tavg3d_dyn_v.GEOS510.20080320_0000.V01.hdf
and I was able to read it into IDL with HDF_BROWSER, which gives info about each data block:
   ** Structure <108eeeb8>, 15 tags, length=152, data length=136, refs=2:
      ...
      LABEL           STRING    'Relative humidity'
      NAME            STRING    'RH'
      ... 
      TYPE            STRING    'FLOAT'
      UNIT            STRING    'percent'

But then if you print out the min and max of the data I got:
    Time      Time from           Date          Time
    Index     1993 (s)       (YYYYMMDD)      (HHMMSS)
   ===============================================================================
       1   480124806.0        20080320        000000

    ### RH min, max:   0.0000000E+00   1.113281   
If it were % it would be 111.3281%. So there is a factor of 100 difference. Can you confirm this?
I believe that RH is unitless for both the 5.0.1 and the 5.1.0 data. I checked a couple of data files that I had created from both data sets:
     date    time  field    min        max  
   20050101 180000 RH     0.000001   1.052381  --> 2x25 file regridded from GEOS-5.0.1 data
   20080101 180000 RH     0.000000   1.055233  --> 2x25 file regridded from GEOS-5.1.0 data
Also, the last version of the GEOS-5 file spec) that I have says RH is %.
For the time being I'll put a line of code into GEOS-Chem to multiply RH by 100 (our algorithm expects RH in %). That is the easiest fix.
Thanks much,
Bob Y.

Rob Lucchesi (rlucchesi@gmao.gsfc.nasa.gov) replied:

Bob,
You are right. RH as written by the model is a fraction, not a percentage. We will have to modify the documentation and metadata in future products to reflect this. Note that the RH derived from the analysis (in the inst3d_met_p product) is a percentage. RH in the MERRA products is also fractional, but the documentation reflects that.
Thanks for the info.
Rob Lucchesi
GMAO

--Bmy 10:11, 1 April 2008 (EDT)

Wet scavenging in GEOS-5

09-Jan-2008

There can be significant differences in the amount of tracer lost to wet scavenging in GEOS-5 as compared to the equivalent run in GEOS-4. Click HERE to view a powerpoint that describes some of the differences.