In recent year, some problems such as health hazard are caused by urban warming. In addition, future urban warming effect will be more severe with the progress of climate change in the future. On the other hand, depopulation trend has started in Japan in recent year. Many problems such as declining efficiency of urban management are worried if present urban structure would be kept in the future. Therefore, compactification of urbanized area is necessary to avoid such problems caused by the depopulation. Compactification of urbanized area includes the discussion "Where urbanized area should be concentrated?" Introducing the viewpoint of mitigating urban warming effect to this discussion is useful to create livable and sustainable urban environment. Furthermore, energy saving caused by reduction of energy for cooling will be expected if air temperature in urbanized area would be reduced by mitigation of urban warming. So, it seems important evaluating social impact such as reduction of CO2 emission caused by air temperature change when we consider conversion of urban structure with mitigating urban warming effect.
This paper made “sea breeze utilization type scenario” in Kanagawa Prefecture as one of the land use scenarios of compact city with mitigating urban warming effect by using “sea breeze effect map” made in the previous paper. Also, “BAU scenario” and “conventional compact city scenario” are made based on urban masterplan of Kanagawa Prefecture. Sea breeze utilization type scenario is evaluated through the comparison among these three scenarios. Firstly, these scenarios are used as an input of numerical calculation and future urban climates in 2040s are predicted by using meso-scale meteorological model WRF (Weather Research & Forecasting) and pseud global warming method. From the results, future air temperature in target area of each scenario are compared and evaluated. In addition, CO2 emissions in Kanagawa Prefecture during summer target period are estimated by using air temperature sensitivity of power consumption in Kanagawa Prefecture to evaluate social impact of sea breeze utilization type scenario. From the comparison of the results, reduction of CO2 emission with air temperature change is evaluated.
The major findings are as follows:
1) Future average air temperature rise by 2040s in urbanized area in Kanagawa prefecture is about 1.6 °C according to calculation result by using WRF model and pseud global warming method. Especially, air temperature rises larger during nighttime than daytime.
2) Diurnal air temperatures in concentrated urban area of sea breeze utilization type scenario tend to be lower than that of conventional compact city scenario. However, nighttime air temperatures tend to be higher in sea breeze utilization type scenario.
3) CO2 emission during summer target period estimated by using air temperature sensitivity of power consumption increases 12.6 % compared to present condition with air temperature rises by 2040s.
4) Reduction of CO2 emission from BAU scenario is larger than 1% in sea breeze utilization type scenario compared to conventional compact city scenario.
According to the results above, sea breeze utilization type scenario seems to be effective to mitigate diurnal urban warming effects and reduce CO2 emission during summer season. However, nighttime air temperature tends to rise in sea breeze utilization type scenario. So, other countermeasures to mitigate nighttime thermal environment are also should be considered in addition to land use planning in sea breeze utilization type scenario.
