I would like to modify green vegetation fraction file of WRF model.
To to this, I firs calculate NDVI from sentinel-2 images using ArcGIS , and then use below equation to calculate GVF: GVFpixel =( NDVI -NDVI0)/( NDVI∞ - NDVI0)
where GVFpixel is the pixel level GVF and NDVI0 and NDVI∞ are constant NDVI values calculated using pixels with bare soil and dense vegetation in the current study domain, respectively. The above equation is for non-urban area. For urban area I should consider urban fraction. So, I should use below equation to modify green vegetation fraction for urban area: GVFpervious 1= GVFpixel / 1-furban where GVFpervious and GVFpixel are pervious- and pixel-level GVF, respectively, and furban represents the urban fraction of the pixel.
My question is how to calculate urban fraction using ArcGIS please? Do you know how to do this.
Look forward to hearing from you. Best wishes,
Dear Setareh Rahimi!
You may use Normalized Difference Built-up Index (NDBI) to map the urban area in your study.
The Normalized Difference Built-up Index (NDBI) uses the NIR and SWIR bands to emphasize man-made built-up areas. It is ratio based to mitigate the effects of terrain illumination differences as well as atmospheric effects.
NDBI = (SWIR - NIR) / (SWIR + NIR)
- SWIR = pixel values from the short-wave infrared band
- NIR = pixel values from the near infrared band
Also, the Normalize Difference Build-up Index value lies between -1 to +1. Negative value of NDBI represent water bodies where as higher value represent built-up areas. NDBI value for vegetation is low.
Reference: Zha, Y., J. Gao, and S. Ni. "Use of Normalized Difference Built-Up Index in Automatically Mapping Urban Areas from TM Imagery." International Journal of Remote Sensing 24, no. 3 (2003): 583-594.
Kind Regards.
Dear Rakesh Kumar ,
So many thanks for your advise, it was helpful.
Kind regards,
Hi,
Kindly refer this link:
https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?t=8738
Best wishes..
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