Hi LB users and developers,
While working with the Urban Weather Generator (UWG) component in Dragonfly, I came across an interesting observation that I would like to share with you.
It appears that the UWG model modifies only a limited subset of weather parameters, specifically, dry-bulb temperature, dew-point temperature, relative humidity, and wind speed. Other environmental variables such as direct normal irradiance, diffuse horizontal irradiance, horizontal infrared radiation, direct normal illuminance, and diffuse horizontal illuminance remain unchanged after applying the UWG transformation.
I have attached an example based on the official Ladybug Tools template to illustrate this behavior.
UWG_challenge.gh (672.8 KB)
However, based on my understanding, these radiation and illuminance variables should also be influenced by changes in temperature and humidity. For instance, in the alternative_weather example, the Zhang-Huang model is used to estimate irradiance values as a function of dry-bulb temperature, dew-point temperature, relative humidity, wind speed, and atmospheric pressure. Furthermore, a review of the Ladybug Core source code indicates that illuminance values are calculated using the Perez model, which also depends on the Zhang-Huang model. For horizontal infrared radiation, empirical models such as the one described in this study are applied.
Given this, I would like to raise the question: should the UWG component be updated to propagate its effects to irradiance and illuminance variables as well? It seems that the current implementation may overlook their interdependence with the meteorological inputs UWG modifies.
I look forward to hearing your thoughts and feedback.
Sincerely,
Behnam