I'm stuck with my large Modis AOD dataset

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duncanwp
Re: I'm stuck with my large Modis AOD dataset

Dear Prof. Torres

I'm sorry to hear that your stuck, CIS should be able to do this task quite easily - what have you tried so far?

I presume you are using Level 2 MODIS data, in which case to aggregate to a daily mean you would need to specify a horizontal grid as well. Assuming a typical layout of MODIS files, you can do this using the aggregate command like so:

cis aggregate :/MYD04_L2/2008/203/*.hdf x=[-180,180,1],y=[-90,90,1] -o 20080721_modis_aod.nc

Here I've taken all the files from the 2008/203 folder (which is the 203rd day of the year - assuming you have mirrored the NASA repository), and aggregated them onto a one degree by one degree grid, so you now have a one day average. You could then simply loop over each day using Python/Bash whichever scripting language you prefer. You would just need to check which variables you want from each file, and specify the right horizontal grid. This will be output to a NetCDF file which CDO can work with automatically.

Alternatively, you can go to your precipitation grid directly using one collocation command:

cis col :/MYD04_L2/2008/203/*.hdf 20080721_precip_file.nc -o 20080721_modis_aod_on_precip.nc

This is assuming the precip files are cf-conformant so that CIS can read them.

Hopefully that helps, if you have any other questions please just ask.

Duncan

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