The UWG failed to run with low temperatures

grasshopper dragonfly
1

Hi there,
I am encountering issues while running the Urban Weather Generator (UWG) simulation. After investigating, I discovered that the simulation fails on days when the temperature in the EPW file is lower than approximately -24°C. By replacing the EPW file with one containing higher temperatures, the simulation runs without any interruptions. I understand that the chosen region is characterized by extremely cold conditions, but I would like to know if there is a solution to this issue. Below is the error code I encountered:

  1. Solution exception:The UWG failed to run:
    UWG model simulation failed.
    Got canyon temperature at -23.246093420283643 C. Something obviously went wrong (UCMDef.py).
    Traceback (most recent call last):
    File “C:\Users\62667\ladybug_tools\python\lib\site-packages\uwg\cli\simulate.py”, line 50, in simulate_json_model
    uwg_model.simulate()
    File “C:\Users\62667\ladybug_tools\python\lib\site-packages\uwg\uwg.py”, line 1354, in simulate
    self.forc, self.geoParam)
    File “C:\Users\62667\ladybug_tools\python\lib\site-packages\uwg\UCMDef.py”, line 288, in UCModel
    ‘wrong (UCMDef.py).’.format(self.canTemp - 273.15))
    Exception: Got canyon temperature at -23.246093420283643 C. Something obviously went wrong (UCMDef.py).
    Any help or suggestions on how to resolve this problem would be greatly appreciated. Thank you!
2

Hi @XINYUXU - this is probably an error checking code from the UWG Matlab code (i.e. the version that I worked on back in 2016) that should have been removed. At the time, I was dealing with numerical convergence issues so had added a check but I probably forgot to remove it and it probably just got copied to the Python version of it. At the time, I was working with warmer weather files so this was an arbitrary value as a quick & dirty way to check when the solution failed to converge.

@chris @SaeranVasanthakumar

1 Like
4

Thanks for your response. I’m using Dragonfly v1.60 with built-in UWG, but the issue persists. This interruption prevents a full EPW file from morphing.I’m still experiencing this problem.

5

As a quick fix for your own set up, use a text editor to open the file ““C:\Users\62667\ladybug_tools\python\lib\site-packages\uwg\UCMDef.py”” and edit the values in line 286 to a different value. The problem is the ‘self.canTemp < 250’ part as the lower threshold so either use something lower like 200 or comment out the section altogether.

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Note for @chris & @SaeranVasanthakumar:
If I remember correctly, this checking is not really necessary at this point anymore as the canyon temperature calculation was changed to an implicit step.

6

Thanks for your help. I’ll work on resolving the issue. If I have more questions, I’ll reach out.

7

Thanks for making us aware of this, @josephyang , and for reporting the issue, @XINYUXU .

I loosened the check to accept temperatures down to -73C, which should accommodate some of the coldest recorded temperatures on Earth:

The fix should be available with the LB Versioner component in a couple of hours or so.