Hi, I am looking for a tutorial that will describe how to model and analyze outdoor space to get how adding things like trees, and changing ground cover will affect thermal comfort - so an urban heat island or UTCI.
I have seen a few approaches but often they appear to not be working properly, for example giving grass being hotter that concrete.
Can any one point me to an approach that has been checked and works properly?
Also: what is the difference between UTCI analysis and Urban Heat Island analysis?
The Universal Thermal Comfort Index (UTCI) is an outdoor thermal comfort metric, whereas the Urban Heat Island (UHI) is just a general term describing the phenomena of average air temperatures in urban areas being warmer then non-urban areas. You probably want to use both, use something like the UWG component in Dragonfly to modify a rural EPW file to account for the UHI, and then use the resulting environmental variables (with some level of modification to account for spatial impacts) in a UTCI calculation.
Now that I think about it, my advice is actually a little outdated, since state-of-the-art efforts in recording climate data via weather files have moved beyond just using regular TMY3/TMY2 files. To learn about state-of-the-art efforts I would recommend reading this conversation[1] which goes into the use of TMYx files for up-to-date weather files that better capture early consequences of climate change, and this thread[2] about ERA5 Reanalysis data that goes into capturing fine-grain spatial data. These weather files can then also be integrated into the workflow I described above.
You should usually find that the surface temperature of grass tends to be lower than asphalt but, if you are comparting grass to high-albedo or low-e concrete, it can definitely be cooler than grass. Also bear in mind that a person standing above asphalt can be cooler than one standing above grass/concrete because more solar energy is reflected up towards the human subject when the ground is lighter.