Modeling Human Thermal Experience in the Urban Microclimate

Human thermal experience is highly influenced by the characteristics of the local environment. Advancing space design and understanding the microclimate are fundamental to achieving a healthy thermal environment. Considering the increasing urbanization and climate change, such concerns will interest a large part of the world population. In this study we used municipal datasets including 3D City Models and Building typology information to build a multi-physics model of the microclimate in Downtown New York City, arriving at temperature and flow fields for the calculation of the human physiological equivalent temperature. A methodology was developed to assess the accuracy of the simulation output by combining weather stations and broadband sensors including airborne and terrestrial infrared imaging systems for surface temperature measurements. We investigated the usefulness of a steady-state versus transient formulation of the flow field and long- and shortwave radiative interactions. We find that the steady-state models, which lack full integration of the thermal capacitance of the urban fabric, do not fully represent how heat is absorbed and stored and released. The steady state formulation of this thermal inertia overestimates pedestrian-level temperatures and overall urban heat retention. It is concluded that transient simulations are required for accurate estimation of climate parameters pertaining to human thermal exposure and the estimation of physiological equivalent temperature.