Effects of vegetation on the urban thermal environment and climate adaptation a case study in hanoi

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY TRAN HUYEN CHI EFFECTS OF VEGETATION ON THE URBAN THERMAL ENVIRONMENT AND CLIMATE ADAPTATION: A CASE STUDY IN HANOI MASTER’S THESIS Hanoi, 2020 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY TRAN HUYEN CHI EFFECTS OF VEGETATION ON THE URBAN THERMAL ENVIRONMENT AND CLIMATE ADAPTATION: A CASE STUDY IN HANOI MAJOR: CLIMATE CHANGE AND DEVELOPMENT CODE: 8900201.02QTD RESEARCH SUPERVISORS: Prof HIROYUKI KUSAKA Prof PHAN VAN TAN Hanoi, 2020 PLEDGE I assure that this thesis is the result of my own research and has not been published The use of other research’s results and other documents must comply with regulations The citations and references to documents, books, research papers, and websites must be in the list of references of the thesis Author of the thesis Tran Huyen Chi ACKNOWLEDGMENTS Being a student of Vietnam Japan University (VJU) and the Master’s Program in Climate Change and Development (MCCD) is one of, if not the, best experience of mine There are a lot of people to whom I would like to express my great appreciation: my supervisor, Prof Hiroyuki Kusaka from the University of Tsukuba, and my subsupervisor, Prof Phan Van Tan from Hanoi University of Science, for instructing and giving me advice for this final project, the professors from MCCD and other programs and universities for providing me a lot of useful knowledge throughout the course, Prof Nguyen Thi Kim Cuc from Thuyloi University for guiding my fieldwork group in Xuan Thuy and inspiring me a lot by her enthusiasm for her work, D&L Technology Integration and Consulting Joint Stock Company and Vietnam Meteorological and Hydrological Administration for providing me meteorological data, people on the Internet for helping me with coding, the sponsors for offering me scholarships, and of course, my family and friends for supporting and encouraging me throughout my study Last but not least, I would also like to extend my thanks to the 3rd intake students of VJU, especially brothers and sisters in MCCD, who are young despite their ages, enthusiastic, and brilliant in their own way, for spending valuable time with me during two years I wish to continue to accompany them in the future I could not mention all on this page, but everyone I met during this two-year course truly gave me great experience TABLE OF CONTENTS CHAPTER INTRODUCTION 1.1 Overview of the study 1.1.1 Background 1.1.2 Significance of the study 1.1.3 Purpose of the study 1.1.4 Scope of the study 1.1.5 Research questions and hypotheses 1.2 Urban thermal environment 1.2.1 Urban area 1.2.2 Urban atmosphere 1.2.3 Urban heat island effect 1.2.4 Climate change and cities 1.3 Urban vegetation and its cooling effects 10 1.3.1 Cooling effects of vegetation 10 1.3.2 Review of studies on the cooling effect of vegetation 12 1.4 Climate of Hanoi 14 1.4.1 Background climate of Hanoi 14 1.4.2 Urbanization in Hanoi 16 1.4.3 Climate change in Hanoi 17 CHAPTER METHODOLOGY 19 2.1 Data collection 19 2.1.1 Air temperature and humidity data 19 2.1.2 Vegetation cover data 22 2.2 Data analysis 23 2.2.1 Tools 23 2.2.2 Calculating air temperature and humidity 23 2.2.3 Calculating green fractions 24 2.2.4 Estimating correlations between green fraction and temperature, humidity and THI 27 CHAPTER RESULTS AND DISCUSSIONS 29 3.1 Air temperature and humidity 29 3.1.1 Changes in air temperature and humidity during the day 29 3.1.2 Monthly mean air temperature and humidity 31 3.1.3 Mean daytime and nighttime air temperature and humidity 34 3.1.4 UHI magnitude 36 3.2 Green fractions 38 3.3 Correlations of the green fraction with air temperature, humidity, and THI 40 CHAPTER RECOMMENDATIONS 49 CHAPTER CONCLUSIONS 50 REFERENCES 53 APPENDIXES 56 LIST OF TABLES Table 2.1 Stations and remarks 21 Table 3.1 Air temperature, relative humidity, and THI classified by green fraction in June 2020 44 LIST OF FIGURES Figure 1.1 Schematic of climatic scales and vertical layers found in urban areas PBL – planetary boundary layer, UBL – urban boundary layer, UCL – urban canopy layer (Oke, 2006, modified from Oke, 1997) .5 Figure 1.2 Illustration of the UHI effect Figure 1.3 Reflection, transmission, and absorption of solar radiation by plant leaves (Brown and Gillespie, 1995, modified by Kong et al., 2017) 11 Figure 1.4 Temperature and precipitation in Hanoi 16 Figure 1.5 Map of Hanoi districts 18 Figure 2.1 Device PAS-OA318 .20 Figure 2.2 Distribution of the study sites The x-axis refers to the longitudes, and the y-axis refers to the latitudes 22 Figure 2.3 Types of vegetation cover The top row refers to the side view of the plant The bottom row refers to the bird’s-eye view of the plant The orange highlights represent the area included in each type of cover .24 Figure 2.4 HSV colormap for OpenCV The x-axis represents H in [0,180), the yaxis represents S in [0,255], the y-axis represents S = 255, while keep V = 255 25 Figure 2.5 Sample of estimating green fraction at Ly Thuong Kiet .26 Figure 3.1 Changes in air temperature and humidity during the day in January 2020 Lines with the same style are the same category 30 Figure 3.2 Changes in air temperature and humidity during the day in June 2020 Lines with the same style are the same category 31 Figure 3.3 Monthly mean air temperature (left) and humidity (right) in January 2020 (Unit: °C and %) The x-axis refers to longitudes, and the y-axis refers to latitudes 32 Figure 3.4 Monthly mean air temperature (left) and humidity (right) in June 2020 (Unit: °C and %) The x-axis refers to longitudes, and the y-axis refers to latitudes 33 Figure 3.5 Mean daytime air temperature and humidity (top) and mean nighttime air temperature and humidity (bottom) in January 2020 (Unit: °C and %) The numbers of locations are the same as in Figure 3.3 The x-axis refers to longitudes, and the yaxis refers to latitudes 35 Figure 3.6 Mean daytime air temperature and humidity (top) and mean nighttime air temperature and humidity (bottom) in June 2020 (Unit: °C and %) The numbers of locations are the same as in Figure 3.4 The x-axis refers to longitudes, and the y-axis refers to latitudes .36 Figure 3.7 Air temperature and UHI between urban sites and outskirts in January (left) and June (right) 2020 at 1:00, 7:00, 13:00, and 19:00 “Outskirts” is the average of Son Tay and Ba Vi “UHI” is equal to “Urban” minus “Outskirts” .37 Figure 3.8 Green fractions in 23 locations (Unit: %) The x-axis refers to longitudes, and the y-axis refers to latitudes .39 Figure 3.9 Hang Quat (left) and Ly Thuong Kiet (right) 40 Figure 3.10 Correlations of green fraction with air temperature, relative humidity, and THI in January 2020 at 14 locations The shaded areas on the horizontal axes refer to the distribution of green fraction, and those on the vertical axes refer to the distributions of mean air temperature, relative humidity, and THI 41 Figure 3.11 Correlations of green fraction with air temperature, relative humidity, and THI in January 2020 during daytime (top) and at nighttime (bottom) at 14 locations The shaded areas on the horizontal axes refer to the distribution of green fraction, and those on the vertical axes refer to the distributions of mean air temperature, relative humidity, and THI 42 Figure 3.12 Correlations of the green fraction with air temperature, relative humidity, and THI in June 2020 at 20 locations The shaded areas on the horizontal axes refer to the distribution of green fraction, and those on the vertical axes refer to the distributions of mean air temperature, relative humidity, and THI 42 Figure 3.13 Correlations of the green fraction with air temperature, relative humidity, and THI in June 2020 during daytime (top) and at nighttime (bottom) at 20 locations The shaded areas on the horizontal axes refer to the distribution of green fraction, and those on the vertical axes refer to the distributions of mean air temperature, relative humidity, and THI 43 Figure 3.14 Correlation models of the green fraction with mean air temperature, humidity, and THI in June 2020 .45 Figure 3.15 Correlation models of the green fraction with mean daytime air temperature, humidity, and THI in June 2020 46 Figure 3.16 Monthly mean temperature and green fraction in the locations classified by districts and categories in June 2020 48 CHAPTER INTRODUCTION 1.1 Overview of the study 1.1.1 Background Hanoi, like other cities in the world, has been facing a rise in temperature due to urbanization and global climate change It is the capital of and the second largest city in Vietnam, with an area of 3,359 km2 and a population of 7.52 million people (as of 2018, according to GSO, 2020) The city has more than a thousand-year long history, but it has significantly changed after the reformation – Doi Moi in 1986 Particularly, during the period of 1990 – 2010, the urban population in Hanoi grew from about 0.9 million to over million people (Labbe, 2010), and the urban land area extended from 50 km2 to 190 km2 due to the conversion of a large area of natural lands and water cover into built-up areas (Doan et al., 2019) Land-use change and anthropogenic heat which have been found to have an impact on the urban heat island (UHI) effect (Kusaka et al., 2000) are factors that have been increasing the temperature in Hanoi (Doan et al., 2019) In addition, global warming is another factor that has been making the city warmer (Lee et al., 2017) As projected by Lee et al (2017), global warming along with land use change will further increase the temperature in the current urban areas in Hanoi by up to 2.1°C in the 2030s, not to mention the impact of anthropogenic heat Temperature rise matters since it may affect human comfort and health High temperatures are uncomfortable for residents, and they can be dangerous as they may cause illnesses such as heat cramps, heat stroke, and even death, especially for young children, the elderly, people with sickness, and people working outdoor Big cities are densely populated, so many people may be affected Illness due to excessive heat can be more serious in moderate regions where people are familiar to cool weather For example, a heatwave in 2003 caused 70,000 deaths in Europe (WHO, 2018 , and a heat wave in 1995 caused 600 deaths in Chicago, US (EPA, 2017) However, even in tropical cities like Hanoi, extremely or long-lasting hot days can still be a serious problem to public health if they exceed the adaptability of the residents It is recorded that in summer many people are hospitalized due to heat-related illnesses The proportion of elderly patients visiting the hospital in June 2020 was about 150% higher than before, and the number of young patients visiting the hospital increased by more than 30% compared to the previous month (An Ha, 2020) Hanoi has also experienced heat-related mortality, for instance, deaths in June 2019 (Thuy Hanh, 2019) In order to prevent negative effects of high temperatures on the residents' health and well-being, methods to mitigate the temperature are required, especially as in Hanoi most people travel outside by motorbikes, which increases the exposure to the sun Taking advantage of ecosystem services is one of the solutions that can be considered Many studies have shown the cooling effects of vegetation, including shading effects and transpiration (Lin and Lin, 2010; Lee et al., 2013; Georgescu et al., 2014) Plant leaves reduce radiation by reflection and transmission They also release water vapor to the air, cooling the ambient air (Brown and Gillespie, 1995) Not only that, but green also makes the landscape more beautiful and visually pleasant For these reasons, increasing vegetation appropriately could be a good solution to temperature rise due to urbanization and climate change in Hanoi among various solutions Research on the effects of vegetation on temperature has been carried out in many cities such as Rosario in Argentina (Coronel et al., 2015), Lisbon in Portugal (Oliveira et al., 2017), Shenzhen in China (Qiu et al., 2017), and Kuala Lumpur in Malaysia (Isa et al., 2018), showing the areas with more vegetation were cooler than the areas with less vegetation According to the study in China by Qiu et al (2017), the cooling effect of vegetation may even be better than water cover Therefore, I would like to discover how green can actually help cool the air and provide better thermal comfort in Hanoi by evaluating the effects of vegetation on air temperature and humidity 1.1.2 Significance of the study There has not been sufficient research on the effects of vegetation on the urban thermal environment in Hanoi so far; therefore, the present study could provide some understanding about this topic The results from the study are expected to provide a case study for the benefits of vegetation in climate change adaptation, contribute to A seasonality relation of vegetation with air temperature, humidity, and THI was also found Vegetation cover was more correlated to air temperature, humidity, and THI in June than in January, meaning that vegetation has more significant effects on the urban thermal environment in summer than in winter Therefore, it is reasonable to increase vegetation cover to cool the environment in summer as it would not make the environment much colder in winter Results in June showed that temperature tended to be lower, and relative humidity tended to be higher in the locations that had more vegetation than in the locations that had less vegetation These results have proven the contribution of vegetation to reduce air temperature and increase relative humidity through shading effects and transpiration A fairly strong correlation of the green fraction with monthly mean air temperature, and a moderate correlation of the green fraction with monthly mean relative humidity were found The correlations of the green fraction with air temperature and humidity were found to be more significant during daytime than at nighttime, because of the lack of transpiration at nighttime, and the restriction of surface radiation due to built infrastructures and tree canopy (Ziter et al., 2019) On average, in June, 15 - 42.5% vegetation can reduce 0.9 - 1.7 °C compared to less than 5% vegetation In general, the THI was also lower in the locations that had higher green fractions, implying that vegetation can provide better thermal comfort, especially during daytime On average, locations with green fractions 9.1 - 42.5% had the THI that was 0.5 - 0.9 lower than the locations with green fractions below 5% To conclude, the study has proven that vegetation can provide a cooling effect in the urban area in summer, and can be one of the climate change adaptation measures in cities The cooling effect of vegetation is more significant during daytime, when many people go out, suggesting that it can help reduce heat-related health problems Therefore, it is necessary to consider the vegetation cover in construction and urban planning, especially in the context of climate change that is expected to warm the city in the next decades The French urban planning is a planning style that should be learned from To increase the green cover while the population keeps increasing, creating a compact city may be a good solution for prospective urban areas in Hanoi 51 Besides, there is also a need to consider measures to use energy efficiently so that it does not warm up the outdoor air temperature too much Despite that the cooling effect of vegetation is significant during daytime, it is limited at nighttime, while the UHI is more significant at nighttime, so there should be other measures to reduce the UHI at night Still, the study has some limitations It only examined January and June in a year, which are not representative of the long-term climate In addition, the research did not consider other factors affecting temperature so the pure effect of vegetation has not been figured out Another problem is probably the use of the THI formula in the research Even though this formula is used in many studies and is known to be proposed by Kyle (1994), I could not find the original paper to check how it was formed, so it may be unlikely that this formula is relevant to the climate of Hanoi Also, the correlation models were not performed very well, and the vegetation cover needed to tackle future warming in Hanoi could not be estimated as initially intended This study is initial research on the effects of vegetation on the thermal environment Further research suggested to be done afterward involves the separation of the pure effect of vegetation from the effects of different factors on the urban thermal environment; the vegetation cover needed to tackle future warming in the city; the effects of vegetation on different scales; and the difference in effects of different types of vegetation and different species of tree 52 REFERENCES An Ha (2020) The number of 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has its value in degrees (over 360 degrees) For example, 0° (or 360°) is red, 60° is yellow, 120° is green, 180° is cyan, 240° is blue, and 300° is magenta Saturation is the intensity of pure color It is usually represented in percentages or between and The higher the saturation, the closer to pure color In contrast, the lower the saturation, the closer to gray Value is the brightness of the color (e.g light blue or dark blue), varying from black to the average saturation of the color Value is represented in percentage or between and Black has a value of 0% HSV can be represented as a cylinder like the figure below HSV cylinder (Source: http://wikipedia.com) In OpenCV, the range of hue is [0, 179], the range of saturation is [0, 255], and the range of value is [0, 255] It is noteworthy that images in OpenCV are BGR, not RGB That is why it is presented in the method section that the images were converted from BGR to HSV 56 Appendix B Tables of air temperature, humidity, and THI in 14 locations in January 2020 Air temperature (°C) Stations Relative humidity (%) Mean Std Min Max Mean Std Min Max Gamuda Gardens 19.7 2.9 14.9 28.5 76.7 12.5 35.3 95.3 Times City 18.8 3.6 13.1 28.2 80.2 11.9 39.3 95.3 Ha Dinh 19.5 3.9 12.4 30.0 77.9 12.3 34.7 96.9 Thai Ha 19.3 3.8 13.1 28.1 79.7 11.1 41.4 95.9 Nguyen Che Nghia 19.8 3.7 13.5 29.7 78.0 12.3 30.5 96.4 Hang Quat 19.8 3.9 13.5 29.8 76.5 12.5 31.1 95.1 Hang Bun 19.8 3.5 13.6 28.4 77.9 11.8 35.7 96.0 Kim Ma 20.0 3.4 14.4 29.7 76.4 11.2 35.7 94.3 Ly Thai To 19.6 3.7 13.6 28.9 79.0 12.3 32.9 96.0 Hoang Hoa Tham 19.7 3.6 13.5 28.4 78.7 11.5 36.3 96.3 1 Tran Quoc Toan Primary School 19.8 3.6 14.0 28.2 78.5 11.3 37.7 94.5 Genesis School 19.9 3.9 13.3 31.5 78.4 12.2 30.7 95.3 Quang An Primary School 20.0 3.5 13.7 28.6 78.6 12.1 31.7 95.5 Trung Hoa Secondary School 19.9 3.7 13.5 30.5 76.8 12.3 30.2 95.0 57 Stations GF (%) Monthly mean Daytime mean Nighttime mean T (°C) RH (%) THI T (°C) RH (%) THI T (°C) RH (%) THI a a a Thai Ha 3.2 19.3 79.7 18.8 19.8 77.4 19.2 18.9 82.3 18.4 Kim Ma 3.5 20.0 76.4 19.3 20.4 74.4 19.5 19.6 78.5 19.0 Hang Bun 19.8 77.9 19.2 20.3 75.4 19.5 19.3 80.6 18.8 Times City 9.1 18.8 80.2 18.3 19.3 77.4 18.7 18.2 83.3 17.8 Hoang Hoa Tham 9.5 19.7 78.7 19.1 20.3 76.1 19.5 19.2 81.4 18.7 Ha Dinh 14.7 19.5 77.9 18.9 20.2 74.9 19.4 18.7 81.2 18.3 Trung Hoa Secondary School 16.4 19.9 76.8 19.2 20.5 74.1 19.6 19.3 79.8 18.8 Quang An Primary School 17.7 20.0 78.6 19.3 20.6 75.5 19.8 19.2 82.0 18.8 Gamuda Gardens 17.8 19.7 76.7 19.1 20.1 74.7 19.3 19.4 78.8 18.8 Genesis School 18.1 19.9 78.4 19.2 20.5 75.4 19.7 19.1 81.6 18.7 Nguyen Che Nghia 18.4 19.8 78.0 19.1 20.4 74.9 19.6 19.1 81.4 18.6 Tran Quoc Toan Primary School 22.4 19.8 78.5 19.1 20.2 76.4 19.4 19.4 80.7 18.9 Ly Thai To 24.9 19.6 79.0 19.0 20.1 76.2 19.3 19.0 82.0 18.6 58 Appendix C Tables of air temperature, humidity, and THI in 23 locations in June 2020 Stations Air temperature (°C) Relative humidity (%) Mean Std Min Max Mean Std Min Max Cau Dien 33.9 2.6 28.0 42.7 60.7 10.0 35.9 82.1 Gamuda Gardens 32.5 2.1 27.9 37.9 66.9 9.6 41.6 84.5 Times City 32.4 3.8 24.6 42.5 68.9 13.5 36.1 93.2 Ha Dinh 33.4 4.3 23.8 43.7 64.9 14.4 32.2 93.4 Ecolife 32.2 3.2 25.6 41.4 69.2 12.3 37.1 90.8 Ly Thuong Kiet 32.3 3.5 24.4 41.3 68.6 13.4 36.5 94.5 Pham Tuan Tai 33.3 3.8 25.0 42.4 64.7 14.1 33.6 95.1 Thai Ha 33.4 3.4 24.1 40.8 66.4 12.7 39.3 95.4 To Hieu 33.9 4.0 25.4 44.1 64.6 14.2 31.7 92.4 10 Nguyen Che Nghia 32.7 3.4 25.4 41.1 67.5 13.3 35.8 93.3 11 Hang Quat 33.8 4.1 24.7 44.3 63.9 14.8 30.7 94.3 12 Hang Bun 33.3 3.3 25.3 40.9 66.0 13.2 36.0 93.6 13 Tran Quang Khai 32.8 3.7 24.6 43.2 68.1 14.5 32.5 96.2 14 Kim Ma 33.6 2.9 26.9 40.8 64.2 11.9 36.1 91.5 15 Ly Thai To 32.9 3.4 25.0 41.5 67.9 13.6 35.2 93.0 16 Hoang Hoa Tham 33.2 3.7 25.6 42.9 65.6 13.8 33.2 94.6 17 Hang Thiec 34.2 4.0 25.3 44.0 60.7 13.1 19.1 80.5 18 Doi Can 34.6 3.0 27.0 41.7 70.2 11.7 43.4 98.6 19 Tran Quoc Toan Primary School 32.9 2.9 25.3 40.0 67.8 12.2 38.3 92.8 20 Le Quy Don Secondary School 33.5 3.3 26.6 40.6 64.8 12.0 39.0 89.1 21 Genesis School 33.6 3.8 24.8 45.1 65.7 14.0 30.7 95.7 22 Quang An Primary School 33.1 3.3 25.8 42.1 66.7 13.0 34.9 91.6 23 Trung Hoa Secondary School 33.0 3.1 26.4 40.6 65.6 12.1 37.0 89.2 24 Nguyen Trai Secondary School 33.0 3.0 26.0 42.4 65.5 12.2 33.2 91.6 59 Stations GF (%) Monthly mean Daytime mean Nighttime mean T (°C) RH (%) THI T (°C) RH (%) THI T (°C) RH (%) THI a a a Hang Quat 2.4 33.8 63.9 30.0 36.1 56.4 30.9 31.2 72.1 28.7 Hang Thiec 2.6 34.2 60.7 29.9 36.5 54.8 31.0 31.6 67.0 28.5 Kim Ma 3.5 33.6 64.2 29.9 34.8 59.8 30.3 32.3 68.9 29.3 Doi Can 3.6 34.6 70.2 31.3 35.8 65.8 31.8 33.2 74.8 30.6 33.3 66.0 29.8 34.9 60.2 30.4 31.4 72.3 28.9 To Hieu 4.8 33.9 64.6 30.1 35.9 58.0 31.0 31.6 71.8 29.0 Times City 9.1 32.4 68.9 29.3 34.6 61.8 30.4 30.0 76.6 28.0 Cau Dien 9.2 33.9 60.7 29.7 34.2 59.5 29.8 33.6 61.8 29.6 Hoang Hoa Tham 9.5 33.2 65.6 29.7 35.0 59.4 30.4 31.2 72.2 28.6 Nguyen Trai Secondary School 9.7 33.0 65.5 29.5 34.3 60.8 30.0 31.7 70.5 28.9 Pham Tuan Tai 15 33.3 64.7 29.6 35.2 58.3 30.4 31.1 71.8 28.6 Ly Thuong Kiet 16.2 32.3 68.6 29.3 34.2 62.2 30.1 30.3 75.7 28.2 Trung Hoa Secondary School 16.4 33.0 65.6 29.5 34.4 60.5 30.1 31.5 71.0 28.8 Quang An Primary School 17.7 33.1 66.7 29.7 34.7 61.0 30.4 31.3 73.0 28.8 Gamuda Gardens 17.8 32.5 66.9 29.2 33.4 63.4 29.6 31.6 70.5 28.8 Genesis School 18.1 33.6 65.7 30.0 35.4 59.7 30.8 31.5 72.2 28.9 Tran Quoc Toan Primary School 22.4 32.9 67.8 29.6 34.2 63.1 30.2 31.5 72.7 29.0 Tran Quang Khai 23.4 32.8 68.1 29.6 34.7 61.6 30.4 30.8 75.2 28.6 Ly Thai To 24.9 32.9 67.9 29.6 34.5 62.1 30.3 31.1 74.1 28.7 Ecolife 42.5 32.2 69.2 29.2 33.7 63.9 29.9 30.6 74.9 28.3 Hang Bun 60 Appendix D Green fractions in the locations (top figures: aerial images of the locations collected from the USGS, except that of Cau Dien from Google Earth, bottom figures: green areas in the locations detected using OpenCV) 61 62 63 64 Appendix E Dunn test results Monthly mean air temperature 2.4 - 4.8% 9.1 - 9.7% 15 - 18.1% 22.4 - 24.9% 42.5% 2.4 - 4.8% 1.000000 0.073553 0.012827 0.009607 0.013220 9.1 - 9.7% 0.073553 1.000000 0.662521 0.376020 0.173617 15 - 18.1% 0.012827 0.662521 1.000000 0.576999 0.251130 22.4 - 24.9% 0.009607 0.376020 0.576999 1.000000 0.464214 42.5% 0.013220 0.173617 0.251130 0.464214 1.000000 Monthly mean THI 2.4 - 4.8% 9.1 - 9.7% 15 - 18.1% 22.4 - 24.9% 42.5% 2.4 - 4.8% 1.000000 0.021947 0.007281 0.055829 0.012284 9.1 - 9.7% 0.021947 1.000000 0.913116 0.868169 0.273036 15 - 18.1% 0.007281 0.913116 1.000000 0.780332 0.284906 22.4 - 24.9% 0.055829 0.868169 0.780332 1.000000 0.241567 42.5% 0.012284 0.273036 0.284906 0.241567 1.000000 Daytime air temperature 2.4 - 4.8% 9.1 - 9.7% 15 - 18.1% 22.4 - 24.9% 42.5% 2.4 - 4.8% 1.000000 0.026026 0.031795 0.028434 0.023260 9.1 - 9.7% 0.026026 1.000000 0.759982 0.882704 0.364346 15 - 18.1% 0.031795 0.759982 1.000000 0.661205 0.262064 22.4 - 24.9% 0.028434 0.882704 0.661205 1.000000 0.434967 42.5% 0.023260 0.364346 0.262064 0.434967 1.000000 Daytime THI 2.4 - 4.8% 9.1 - 9.7% 15 - 18.1% 22.4 - 24.9% 42.5% 2.4 - 4.8% 1.000000 0.027524 0.028108 0.086683 0.039353 9.1 - 9.7% 0.027524 1.000000 0.810299 0.782055 0.472676 15 - 18.1% 0.028108 0.810299 1.000000 0.936490 0.375193 22.4 - 24.9% 0.086683 0.782055 0.936490 1.000000 0.379775 42.5% 0.039353 0.472676 0.375193 0.379775 1.000000 65 ...VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY TRAN HUYEN CHI EFFECTS OF VEGETATION ON THE URBAN THERMAL ENVIRONMENT AND CLIMATE ADAPTATION: A CASE STUDY IN HANOI MAJOR: CLIMATE CHANGE... thermal environment 1.2.1 Urban area There are many ways to define urban areas In Vietnam’s Law on Urban Planning (2009), an urban area is defined as an area with a high density of population mainly... vegetation in climate change adaptation, contribute to policy-making in urban planning, especially in the context of climate change, and also contribute to green conservation in urban areas 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