Hi @julia_dba
If you are talking about calculating MRT from measurements, you would need to follow the six direction integral method and use sensors that give you both incoming shortwave radiation and longwave radiation. Then you would use an equation like that below to calculate the shortwave and longwave components of MRT (K is the shortwave part, L is the longwave part):
from this paper: Aviv, D., Guo, H., Middel, A., & Meggers, F. (2021). Evaluating radiant heat in an outdoor urban environment: Resolving spatial and temporal variations with two sensing platforms and data-driven simulation. Urban Climate, 35, 100745. Redirecting
You can also predict the shortwave and longwave MRT using the Honeybee UTCI Comfort Map component and you can find the equations for both in the source code.
The shortwave equations are drawn from this paper Arens, E., T. Hoyt, X. Zhou, L. Huang, H. Zhang and S. Schiavon. 2015. Modeling the comfort effects of short-wave solar radiation indoors. Building and Environment, 88, 3-9. Redirecting Modeling the comfort effects of short-wave solar radiation indoors
longwave involves calculating surrounding surface temperatures and weighting by the view factors. Id recommend checking this thread if you want an in depth explanation.