The Maximum Cooling Distance parameter has two functions, namely (i) to determine the distance from which large green spaces (>2 ha) have an extra cooling effect, and (ii) to define the size of the area where the sum and calculation of the vegetation pixels (greenspace) is made. Is that correct?

Therefore, with a smaller cooling distance fewer greenspaces will qualify as larger than 2 ha, whilst larger cooling distances will increase the likelihood of having vegetation patches larger than 2 ha.

But shouldnâ€™t these two factors be independent? How can I reliably estimate cooling distances if the amount of eligible greenspace changes according to the cooling distance used?

If I understand correctly, this is a limitation of the model. I would like to know if there is a way to solve or minimize this.

Hello @jv_martinelli ,

I will ask our science team to weigh in here, but I wanted to clarify a couple of things:

First, on the issue of the 2 ha area, one of the modelâ€™s uses for the maximum cooling distance parameter is to define the search radius for greenspace pixels. If the total greenspace area within the search radius is >= 2 ha, then it is treated as though it is near a large area of greenspace. As stated in the Userâ€™s Guide:

The model does not test whether green spaces are contiguous. Thus, many small green spaces within the search distance will have the same effect on urban heat mitigation as a single large green space of the same area within the search distance.

Second, you mention in your post a question of an â€śextra cooling effectâ€ť for large green spaces. As you can see in the Userâ€™s Guide, there is no extra cooling taking place if a pixel is near a large park. Instead, the only question relating to greenspace area is how much greenspace area exists within the maximum cooling distance.

Because this conditional is so simple when calculating HM_i, I think itâ€™s acceptable here to not have the model differentiate between the maximum cooling distance and the search radius.

As far as how to estimate maximum cooling distance, there is some guidance in the userâ€™s guide about this, but please let us know if this isnâ€™t sufficient to answer your question.

Hope this helps!

James