[gradsusr] MODIS AEROSOL PRODUCTS

[Joshua Ngaina]

Thanks guys for your response. I took time to try all your suggestions and
learnt something new in one way or another. Jennifer's suggestions really
worked in my case.

regards

Joshua


On Wed, May 29, 2013 at 7:15 PM, Jennifer Adams <jma at cola.iges.org> wrote:

> If a netcdf file doesn't have a time dimension, GrADS will assign a
> default time of 00z01jan0001 to the file. That message is not an error, it
> is a warning -- the file was opened successfully. If you want the default
> time to be something else, use a simple xdfopen-style descriptor to assign
> a time. If you want to merge files over the time dimension, you can use
> templating with the CHSUB option -- mapping each file to its particular
> time -- the strings in the filenames are not readily interpreted, so the
> usual date string substitutions won't work.
>
> http://iges.org/grads/gadoc/SDFdescriptorfile.html
> http://iges.org/grads/gadoc/templates.html
>
> --Jennifer
>
> On May 29, 2013, at 8:08 AM, Joshua Ngaina wrote:
>
>
> *Dear All,
>
> *
> *I have daily MODIS aerosol products (Small mode fraction).
>
> *
> *I wanted to merge these files using CDO but it seemed the files were not
> merged.  *
>
> met at met-HP-Compaq-6000-Pro-MT-PC:/media/BERTH/MODIS_DAILY$ cdo mergetime
> *.nc ALLMOD08.nc
> cdo mergetime: Processed 4147200 values from 64 variables over 32
> timesteps. ( 0.18s )
> *
> So to check one of the files, I used grads and I got this error: DF file
> has no discernable time coordinate -- using default values*.
>
> ga-> sdfopen
> MOD08_D3.A2001001.051.2010286151047.pscs_000500504418.Optical_Depth_Ratio_Small_Land_And_Ocean_Mean.G3.nc
> Scanning self-describing file:
> MOD08_D3.A2001001.051.2010286151047.pscs_000500504418.Optical_Depth_Ratio_Small_Land_And_Ocean_Mean.G3.nc
> SDF file has no discernable time coordinate -- using default values.
> SDF file
> MOD08_D3.A2001001.051.2010286151047.pscs_000500504418.Optical_Depth_Ratio_Small_Land_And_Ocean_Mean.G3.ncis open as file 1
> LON set to 0 360
> LAT set to -89.5 89.5
> LEV set to 0 0
> Time values set: 1:1:1:0 1:1:1:0
> E set to 1 1
> ga-> q file
> File 1 :
>   Descriptor:
> MOD08_D3.A2001001.051.2010286151047.pscs_000500504418.Optical_Depth_Ratio_Small_Land_And_Ocean_Mean.G3.nc
>   Binary:
> MOD08_D3.A2001001.051.2010286151047.pscs_000500504418.Optical_Depth_Ratio_Small_Land_And_Ocean_Mean.G3.nc
>   Type = Gridded
>   Xsize = 360  Ysize = 180  Zsize = 1  Tsize = 1  Esize = 1
>   Number of Variables = 2
>      optical_depth_l  0  y,x  Aerosol Optical Thickness at 0.55 microns
> for both Ocean (best) and Land (corrected): Mean
>      optical_depth_r  0  y,x  Ratio of small mode aerosol optical depth at
> 0.55 micron for both land and ocean: Mean
> *
> *
> *I also checked the merged netcdf file *
>
> ga-> sdfopen ALLMOD08.nc
> Scanning self-describing file:  ALLMOD08.nc
> SDF file has no discernable time coordinate -- using default values.
> SDF file ALLMOD08.nc is open as file 1
> LON set to 0 360
> LAT set to -89.5 89.5
> LEV set to 0 0
> Time values set: 1:1:1:0 1:1:1:0
> E set to 1 1
> ga-> q file
> File 1 :
>   Descriptor: ALLMOD08.nc
>   Binary: ALLMOD08.nc
>   Type = Gridded
>   Xsize = 360  Ysize = 180  Zsize = 1  Tsize = 1  Esize = 1
>   Number of Variables = 2
>      optical_depth_l  0  y,x  Aerosol Optical Thickness at 0.55 microns
> for both Ocean (best) and Land (corrected): Mean
>      optical_depth_r  0  y,x  Ratio of small mode aerosol optical depth at
> 0.55 micron for both land and ocean: Mean
>
> *I also noted that the dimension of both files were the same.
>
> *
> *My major problem is with many files of this type, How do I merge this
> files for analysis with GrADs. Please advise
> *
> *
> *
> *
> Regards and Thanks,*
>
> Joshua Ngaina
>  _______________________________________________
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> gradsusr at gradsusr.org
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>
>
> --
> Jennifer M. Adams
> IGES/COLA
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705
> jma at cola.iges.org
>
>
>
>
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