Chen Yi Sun

Surface heat balance analysis of Tainan City on March 6, 2001 using ASTER and Formosat-2 data

The urban heat island phenomenon occurs as a mixed result of anthropogenic heat discharge, decreased vegetation, and increased artificial impervious surfaces. To clarify the contribution of each factor to the urban heat island, it is necessary to evaluate the surface heat balance. Satellite remote sensing data of Tainan City, Taiwan, obtained from Terra ASTER and Formosat-2 were used to estimate surface heat balance in this study. ASTER data is suitable for analyzing heat balance because of the wide spectral range. We used Formosat-2 multispectral data to classify the land surface, which was used to interpolate some surface parameters for estimating heat fluxes. Because of the high spatial resolution of the Formosat-2 image, more roads, open spaces and small vegetation areas could be distinguished from buildings in urban areas; however, misclassifications of land cover in such areas using ASTER data would overestimate the sensible heat flux. On the other hand, the small vegetated areas detected from the Formosat-2 image slightly increased the estimation of latent heat flux. As a result, the storage heat flux derived from Formosat-2 is higher than that derived from ASTER data in most areas. From these results, we can conclude that the higher resolution land coverage map increases accuracy of the heat balance analysis. Storage heat flux occupies about 60 to 80% of the net radiation in most of the artificial surface areas in spite of their usages. Because of the homogeneity of the building roof materials, there is no contrast between the storage heat flux in business and residential areas. In sparsely vegetated urban areas, more heat is stored and latent heat is smaller than that in the forested suburbs. This result implies that density of vegetation has a significant influence in decreasing temperatures.

Vegetation as a Material of Roof and City to Cool down the Temperature

A large amount of research has been published in Taiwan on the reduction of the urban temperature for different strategies. The most important strategy for reducing ambient temperature is increasing green roofs or green spaces in city. For analyzing the effect of the vegetation on the thermal environment, this paper collects temperature and humidity data from two building roofs, one park and two streets which are located within same area and tries to analyze the thermal influence of vegetation in study area. The result of this research shows that the maximum cool effect of green roof was -1.60 °C and the maximum temperature difference between park and street was -2.00 °C. Therefore, it can also provide useful data to governments for calculating the environmental benefit if they carry out a green space and green roof policy.

Passenger thermal perceptions, thermal comfort requirements, and adaptations in short- and long-haul vehicles

While thermal comfort in mass transportation vehicles is relevant to service quality and energy consumption, benchmarks for such comfort that reflect the thermal adaptations of passengers are currently lacking. This study reports a field experiment involving simultaneous physical measurements and a questionnaire survey, collecting data from 2,129 respondents, that evaluated thermal comfort in short- and long-haul buses and trains. Experimental results indicate that high air temperature, strong solar radiation, and low air movement explain why passengers feel thermally uncomfortable. The overall insulation of clothing worn by passengers and thermal adaptive behaviour in vehicles differ from those in their living and working spaces. Passengers in short-haul vehicles habitually adjust the air outlets to increase thermal comfort, while passengers in long-haul vehicles prefer to draw the drapes to reduce discomfort from extended exposure to solar radiation. The neutral temperatures for short- and long-haul vehicles are 26.2°C and 27.4°C, while the comfort zones are 22.4–28.9°C and 22.4–30.1°C, respectively. The results of this study provide a valuable reference for practitioners involved in determining the adequate control and management of in-vehicle thermal environments, as well as facilitating design of buses and trains, ultimately contributing to efforts to achieve a balance between the thermal comfort satisfaction of passengers and energy conserving measures for air-conditioning in mass transportation vehicles.

Comparison of surface heat balance in three cities in Taiwan using Terra ASTER and Formosat-2 RSI data

Abstract In order to investigate the influences of the city scale, usage, topography, and climate on surface heat balance, the authors compared the surface heat balance for three urban areas in Taiwan, namely, Kaohsiung City, Taichung City, and Tainan City, estimated using ASTER and Formosat-2 data. The net radiation was in a similar range in all three study areas because the cities are in close proximity to each other. Tainan City released 60–70% of the sensible heat flux of the other cities because of its smaller size. Taichung City, which is located in a basin, exhibited the largest sensible heat flux, due to the radiation cooling during the night before the observation. Anthropogenic heat discharge clearly decreased the storage heat flux in certain industrial areas in Kaohsiung City and Taichung City, while the small scale urban functions moderated the variation of storage heat flux in Tainan City. These results imply that the terrain around a given city as well as the scale of urban activity significantly affect the heat balance in the cities.

A study in the relationship between greenery of urban parks and bird diversity in Tainan City, Taiwan

Green space is important for the maintenance of the ecological dimension of a sustainable urban landscape. Therefore, in order to figure out the relationship between the greening of urban parks and bird diversity, we used 5 avian ecological diversity indexes, such as Species richness, Abundance, ShannonWeiner diversity index, Evenness, and Margalef’s richness indices, to evaluate the functionality of different types of urban parks. Therefore, birds in 17 parks were surveyed with the circular-plot method from August of 2004 to April of 2005; meanwhile, the greening level of urban park of Tainan city in Taiwan was measured by remote sensing method. As the result, overall there was higher bird species richness in higher greening level parks. Our findings emphasize the importance of urban park with abundant greening to maintain high ecological diversity. Thus, we suggest that increasing greening level of urban parks can promote the bird diversity in urban area.

The Relationship Between Urban Greening and Thermal Environment

In this paper, the traverses survey was conducted to explore both the severity of urban heat island effect and cooling impacts of green areas at macro-level in Tainan Metropolis Region. Urban temperature distribution was mapped relying on data derived from the mobile survey. On the other hand, the sense of FORMOSAT-2 satellite in study area was employed to calculate the greening index, Normalize Different Vegetation Index (NDVI), of the research area by remote sensing technology. The objective of this study is to investigate the relationship between urban greening and thermal environment in Tainan metropolis region and to discuss the effectiveness that the citys greening have brought about to lessen urban temperatures and to dampen the heat island effect. This paper demonstrates the relationship existing between urban greening and thermal environment in order to explore a method to mitigate urban heat island effect and energy consumption. Knowledge on these relationships can be used by planners to recommend tree planting programs and to evaluate the need for new or revised urban design and landscaping policies for mitigating the adverse thermal effects of urban geometry, building mass and poor landscape layouts.

Green Roof as a Green Material of Building in Mitigating Heat Island Effect in Taipei City

A large amount of research has been published in Taiwan on the reduction of the urban temperature for different strategies. The most important strategy for reducing ambient temperature is increasing green space in city. For analyzing the effect of the vegetation on the thermal environment, this paper collects temperature data from one green roof and one normal roof which are belong to a same office building to analyze the thermal influence of vegetation. The result of this research shows that in summer the maximum cool effect of green roof was -1.60 oC and -0.26 oC in average. Therefore, it can also provide useful data to governments for calculating the environmental benefit if they carry out a green roof policy in mitigating heat island effect in the future.

The Thermal Influence of Green Roofs on Air Temperature in Taipei City

During the last decade, a large amount of research has been published in Taiwan on the reduction of the urban heat island effect for different strategies. The most important strategy for reducing ambient temperature and mitigating the heat island effect is to encourage citizens to build green roofs on their buildings. For analyzing the effect of a green roof on the thermal environment, this paper collects temperature and humidity data from two building roofs that have different greening levels and tries to analyze the thermal influence of a green roof on air temperature in Taipei City. The results of this research can give citizens an idea what kind of thermal environment they can benefit from; moreover, it also can provide useful data to governments for calculating the environmental benefit if they carry out a green roof policy.

Designing a Sustainable Planting Module for Extensive Green Roofs under the Tropical Climate.

Heat from solar radiation contributes to the high energy usage in the tropical climate regions. Extensive green roofs are well known efficient tools for heat insulation. This study designs a module system that is easy to implement and requires low maintenance for the extensive green roofs. The module system combined planting substrates and plants within a planting container which achieves the objectives, namely, light weight, easy shipping, good drainage, UV resistance, high water retention, and air permeability.

A Study to Assess Shade in Tainan City for Thermal Comfort

This study examined “EEWH-HI” standards of shade in Tainan, and used rain and the sun as indicators to verify The Plan of Good Looking Corner to improve urban thermal comfort levels on the roads. The Plan of Good Looking Corner in Tainan was ran by the Tainan City Government for schools, offices, green spaces, squares, communities, and other public spaces, to create corners of green in order to beautify and improve the overall urban landscape. This study selected 173 locations to conduct assessments for shade indicators from the rain and sun. Statistical analysis, ANOVA, Regression Analysis, and the Correlation Coefficient method were applied to clarify the impact factor effects of urban shade and thermal comfort to prepare final recommendations.