Cool Roof Potential in Tokyo for Mitigating boiling Summer Heat: its Cost and Benefit
Abstract
In 2018, Japan experienced the record breaking number of heat stroke patients and more than 90 thousand citizens were raced to hospital. Lately summer heat has been problematic more and more in many of Asian mega-cities in terms of health of citizens, the increase of energy demands for air condition, and labor management of outworkers.
Urban heat environments are a combined result of the global warming and urban heat island (UHI) effects. Although a local municipality's efforts cannot hinder the global warming, UHI can be weakened by appropriate urban planning so many of effective heat mitigation methods have been introduced. Among them, cool roof with high reflective painting seemed to be one of the best solutions, which demonstrates effective reduction of urban air temperature with no running cost unlike the other mitigation techniques. Although many numerical studies on the cool roof applied to various cities have been reported, many of them assumed uniform and homogeneous urban forms in their simulations. Therefore, the performance of cool roof seems not to be correctly assessed in the past studies. In addition, using unrealistic urban parameters is unable to discuss the cost of cool-roof installation necessary for achieving desirable decrease of air temperature. We simulated the effect of the cool roof installation in Tokyo Metropolitan area using WRF model with single-layer urban canopy model, which is modified so that the actual urban parameters such as plane area density, roughness length for momentum, sky view factor, as well as anthropogenic heat emission, are incorporated in the simulation. The cool roof can decrease summer air temperature over Tokyo by 2 K on average if all the houses and buildings are altered to cool roofs, which cost approximately 2 billion dollars but reduce electricity demands by 3,200,000 kW per day. The further cost-benefit analysis on the installation of cool roof in Tokyo will be presented.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC11C..05N
- Keywords:
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- 0493 Urban systems;
- BIOGEOSCIENCES;
- 0231 Impacts of climate change: agricultural health;
- GEOHEALTH;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE