Vietnam (Socialist Republic of Viet Nam) is a rapidly developing country. The recent growth rates of the economy and population are about 6.0 % and 1.1 %, respectively. Under such a social situation, the sprawls of urban areas are progressing and many city master plans have been proposed in Vietnam. Recently, a city master plan was proposed for Vinh city, the capital of Nghe An Province, located in the north-central part of Vietnam. The proposed city master plan targets the year of 2030 with a population of 900,000 and the total planning area covers an area of approximately 250 km2.
In this study, future projections of the thermal environment in the urban districts in Vinh city for a month of June (hottest month) in the 2030s were performed by introducing the proposed city master plan. The future projections were carried out using a regional atmospheric model, the Weather Research and Forecasting (WRF) model, combined with a pseudo global warming method. The effect of the introduction of the proposed city master plan on the future thermal environment (air temperature and heat stress index) in the urban districts was quantitatively examined by comparing with the present land use case. Moreover, two modified city master plans by changing the arrangement (northern or southern concentration) of the new urban districts were introduced, and the effects of the modifications on the future thermal environment in the urban districts were also investigated.
The space-averaged (over the whole urban district) and monthly-averaged (during June in the 2030s) temperature difference between the cases with and without the introduction of the proposed city master plan is 0.25 °C. This is considerably smaller than the temperature increase by the global warming in the 2030s projected in this study (1.74 °C). However, the small temperature difference cannot be negligible considering the fact that the increase in the global average surface temperature over the period from 1880 to 2012 was 0.85 °C. Therefore, active actions to mitigate the temperature increase due to the introduction of the proposed city master plan will be necessary.
In the case with the northern or southern concentration of the new urban districts in the proposed city master plan, the space-averaged and monthly-averaged (during June in the 2030s) temperature in the northern or southern new urban districts is higher than that in the original city master plan. From the viewpoint of thermal environment, the original city master plan, in which the new urban districts are decentralized in both northern and southern parts of the planning area, is better than the two modified plans (northern or southern concentration of the new urban districts).
