Question about Calculation Method in Invest Urban Cooling Module (cc_park_ini.tif)

[GuohuaHu]

I am using the Invest Urban Cooling module and noticed something strange when checking the intermediate results. The cc_park_ini.tif file seems to be calculated using green_area with an exponential distance weighting, rather than using cci. According to the documentation, the formula should be:

$CC_{park_i}=\sum_{j\in\ d\ radius\ from\ i} g_j \cdot CC_j \cdot e^{\left( \frac{-d(i,j)}{d_{cool}} \right)}$

However, after further inspection, I found the following code snippet in the source on GitHub:
https://github.com/natcap/invest/blob/main/src/natcap/invest/urban_cooling_model.py#L524

green_area_decay_kernel_distance = int(numpy.round(
        float(args['green_area_cooling_distance']) / cell_size))
cc_park_raster_path = os.path.join(
        intermediate_dir, f'cc_park{file_suffix}.tif')
cc_park_task = task_graph.add_task(
        func=convolve_2d_by_exponential,
        args=(
            green_area_decay_kernel_distance,
            task_path_prop_map['green_area'][1],
            cc_park_raster_path),
        target_path_list=[cc_park_raster_path],
        dependent_task_list=[
            task_path_prop_map['green_area'][0]],
        task_name='calculate T air')

This seems to indicate that green_area is being used in the calculation, not cci. Could I be misunderstanding the code? I would appreciate some clarification.

[davemfish]

Hi @GuohuaHu , thanks for bringing this up. I agree that this seems like an error. As it is, cc_park.tif is simply an exponential decay of the green area map, which is a binary mask. It is not a product of cc.tif at all.

For the sample data,
cc.tif (cooling capacity) has a range of values from (0.138 - 0.839), while
cc_park.tif (allegedly, the exponentially decayed cooling capacity index, due to proximity to green areas) has a range of values from (0.0006 - 0.0041).

This does not make sense to me. @chrisnootenboom or @jagoldstein , would you be able to confirm that the cc_park.tif intermediate results are not logical?