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Green vegetation fraction modification file

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adriana

New member
Dear all,
I need to modify WRF green vegetation fraction file for January 2021. So, I calculated NDVI for each month of the year 2021 and then applied the below equation to compute the green vegetation fraction :
GVF = (NDVI-NDVImin)/(NDVImax -NDVImin)
NDVImin ------> minimum value between 12 months of the year 2021
NDVImax ------> maximum value between 12 months of the year 2121
NDVI -------> NDVI value for month January 2021
After passing all these steps, the result was weird!
In some areas there are overestimations. I wonder where I did a mistake? Please kindly advise me in this regard.
The output and model default files are attached.
Thanks in advance,
Kind regards,
 

Attachments

  • gvf-10meter.png
    gvf-10meter.png
    168.1 KB · Views: 366
  • gvf-default.png
    gvf-default.png
    63.6 KB · Views: 366
Hi,
Can you be more specific with what you modified? Which files did you modify? If you can attach the modified files, that would be even better. And for the plots you're attached, what file are you plotting from? Thanks!
 
Hi kwerner,
I first calculated NDVI using MODIS raster files in ArcGIS. After that using ArcGIS to calculate min and max for 12 months of the year 2021.
used GVF = (NDVI-NDVImin)/(NDVImax -NDVImin) to calculate green vegetation fraction (GVF) for the month of January 2021. In addition, used convert-GeoTIFF to convert the gvf-raster file to binary. Then replace the produced files (Attached) in WPS_GEOG.
The file with the title: "green-fraction" is the one I modified, and the second one with this title: "MODIS FPAR" is model default.
Many thanks,
 

Attachments

  • gvf-modis.zip
    2.4 MB · Views: 33
Hi,
Can you try plotting your modified data tiles with the attached Python script? To use this script, you'll need to make sure you have python, numpy, and matplotlib installed, and then run with the following syntax:
Code:
python plot_tile.py path_to_tile/tile

You may need to make some modifications to the script for your particular dataset. The script will create a *.png file that you can view. Make sure that the image looks like what you would expect, and that it's not upside down or mirrored from what it should be.
 

Attachments

  • plot_tile.py
    923 bytes · Views: 29
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