Help with Eto definition for urban cooling

Hi - please help me to finally understand the role of ETo in the UC model!

after referencing these other questions (the 2nd of which is mine)

  • Doubts about urban cooling model
  • Urban cooling: advice on scenario generation
  • Reference evapotranspiration raster data

I read in the userguide :

  • Reference evapotranspiration varies with elevation, latitude, humidity, and slope aspect

and i read at fao

  • …reference evapotranspiration, denoted as ETo. The reference surface is a hypothetical grass reference crop etc etc

So whatever value I apply, whether its from a local rural site or within my urban location, it is likely to be a single value across my small (15km2) AOI. is that correct?

In that case when the normalized version is used for ETi, ETo/Etmax will always be 1 and Eti = kc

is that correct? But this makes it seem like Eto has no purpose!

So what am i misundestanding?!!? please help!


This looks like a duplicate of Urban Cooling and the Eto layer (and I’m sorry for the delay in getting back to you on it!), so I’ll close this topic.