Virtual Campus: A Local-Scale and Microscale Climatic Field Experiment in the Tropics

Since the Industrial Revolution, a considerable portion of the world population has been concentrating in cities. As a consequence, larger urban areas and taller buildings have been developed to host these growing agglomerations of inhabitants. Among all the cities of the world, Singapore has the third densest population. Thus, a climatic phenomenon like the Urban Heat Island (UHI) effect, which results from urbanization, has been monitored by authorities of this region for several years, due to its negative effect on outdoor thermal comfort and building energy use. To address this concern, the Virtual Campus field experimental campaign was conducted for a period of one year to collect measurements of weather conditions at the local scale and microscale in the campus of the National University of Singapore (NUS). From these measurements, it is expected to certify the reliability of predictions made by various simulations models about the influence of buildings, street pavements, and traffic on weather conditions in the tropics.

At the local scale, for validating the Integrated Multiscale and Multiphysics Urban Microclimate Model (IM4), 20 micro weather stations were installed across the Kent Ridge Campus of NUS, captured typical urban features (urban canyon, dense tree area, open field, etc.), continuously recorded the microclimate data with 7 parameters and display them on a remote monitoring platform. In the same time, geographical information system map and 3-dimensional model were constructed for extracting urban morphology parameters. Five regression models were investigated for prediction of outdoor air temperature (daily maximum, minimum, average, daytime average and nighttime average temperature).The analysis of variables showed greenery played crucial role in the mitigation of both daytime and night-time UHI. Pedestrian level wind flow was helpful in heat release in the daytime. High-rise buildings provided self-shadowing to reduce ambient air temperature but higher SVFwas harmful to heat release in the night-time.

To measure weather conditions at the microscale, a meteorological tower was subsequently operating in two locations of the NUS campus: the School of Medicine and Kent Vale. The former site essentially consists of high-rise office buildings or laboratories, where various meteorological sensors were installed in a street canyon to measure:

• the vertical stratification of air temperature and humidity;
• the motion of air flow over three dimensions;
• the surface temperature of street pavements and building walls; and
• the incoming and outgoing radiations of street pavements in the range of shortwaves and longwaves.

After the operation of the meteorological tower in the School of Medicine, all these measurements were then repeated in the site of Kent Vale. In this residential area, indoor measurements of heat fluxes, wall surface temperature, and air temperature were made additionally.