I was simulating IR BTs over land using CRTM 2.4.0 and found that for the same type of land classification, using IGBP and USGS IR emissivity files can generate different land surface emissivity. For example, for grassland (10 in IGBP and 7 in USGS), the emissivity derived from IGBP is about 0.92 for 3.7microm wavelength but is about 0.84 when using USGS. However, for the type of urban and build-up, they generate the same emissivity value. Can anybody help me figure this out, please?
P.S. I used the same profile and did not set soil and vegetation types.
The short answer is that you should expect two different databases to provide different results. There’s no requirement of consistency between the two databases. Is there a reason that you expect them to be identical?
Generally, one selects that table that works best for their requirements. We’re a small team, so we’ll be happy to accept new methodologies / tables to include in CRTM, but we don’t always have the bandwidth to create new LUTs or to improve / update existing ones.
Hi, Benjamin. Thank you for your reply!
I have to admit that I did not quite understand the emissivity databases before, therefore I assumed they share the same LUT. Thank you again for helping me out.