Research on the Water Balance and Energy Balance of a Green Roof through Measurement, Simulation, and Investigation(1/3)

The alternation of land cover due to urban expansion increases the impervious area and inhibits the processes in the natural water cycle such as evapotranspiration and infiltration It causes the changes in the land-atmosphere interaction, the surface water, and the ground water. The urban area in Taiwan is highly developed and is vulnerable to the frequent extreme hot weather and flood events. It is urgent to investigate the effects of the adaptation strategies on the changes in the land-surface hydrological and heat fluxes. The policies of green roof subsidy that are actively promoted in recent years raise the related industries, increasing the needs of investigating the actual function of green roof in the urban area. Many studies have proofed the functions of green roof in retaining rainwater and adjusting ambient temperature. However, the functions of green roof vary with the environment and conditions. The findings of the previous research may not be applicable to the cases in Taiwan, and the number of the long-term studies in green roof measurement and model validation are still limited. Therefore, a three-year research progress is proposed in this study. In the first year, the green roof module and measurement system is built. The continuous observation is conducted, and the characteristics of water balance is analyzed, to clarify the feature of evapotranspiration and the runoff as well as the water consumption of the plant. In the second year, the energy balance of the green roof and its thermal effect on the building below are investigated. Moreover, the latent heat of green roof is parameterized based on the results of measurement and investigation. The outcomes of the first two years are integrated in the third year to develop a land surface process model and to conduct sensitivity analysis of the water and energy balance and the meteorological factors, providing a tool for comprehensively quantifying the water and the energy balance of a green roof. The results of the three-year project support the government-promoted policies of the low-carbon cities and sponge cities as well as the setup of the water resources Internet of Things (IoT) on the civil IoT platform, in addition to the continuous measurements and model of a green roof.