This dissertation presents, on the one hand, advancements of the scientifically well-established microclimate model ENVI-met that will allow more accurate microclimate modeling and, on the other hand, a broad range of model application studies to provide insights for the urban climate community and support sustainable urban planning in the future. Advancements feature the so-called Indexed View Sphere scheme and Advanced Canopy Radiation Transfer module which both improved radiation modeling accuracy in general. Following a model validation study in Hong Kong, new mean radiant temperature calculation schemes are implemented in the model. Furthermore, a Lagrangian Stochastic Particle Trajectory Model is presented which enables backwards-tracking of particle trajectories for complex urban environments. Aside from these advancements, ENVI-met was applied in an air quality modeling study that examined particulate matter expositions of children in urban environments. Furthermore, the model was used to investigate a new specific heat stress mitigation measure called super cool roofs (SCR) featuring a very high albedo and emissivity. Both, sensitivity studies and case studies on micro- and mesoscale examined the SCR cooling effect on pedestrian-level air temperatures.