Cooling the Urban Environments and its Impact on Climate Change in Informal Settlements through Outdoor Thermal Comfort (Case Studies: Aa’melli, Ghaleh Sakhteman and Hojjat Neighborhoods of Mashhad)

The climate becomes warmer than ever before, as evidenced by numerous observations and modeling that has in turn created a warming climate in cities. Therefore, various climate change projects and attention to heatwaves in recent centuries have been considered and the increase in population and its activities in various fields have caused problems such as heatwaves around the world. In addition, changing the pattern of occurrence of these changes and their unpredictability has led to an increase in the number of them in cities and to reduce concerns and adapt to these risks in various aspects of urban life, especially human health, to create sustainable urban forms. This phenomenon has caused the death of thousands of people in the world, and one of the important reasons for this is the flaw of the cities to deal with the increase in heatwaves. While different changes and global warming can affect urban areas, urban areas can also exacerbate these changes. Rising urbanization rates and people's desire to live in cities have led to higher urban temperatures than their surroundings. Studies show that a city with a population of one million people has experienced an increase in temperature between 1 and 12 degrees. This increase in temperature is due to the structure of cities, which has many negative effects and consequences for cities, so urban environments should be planned and designed in such a way as to improve the health of individuals and thus the presence in public spaces of cities. Urban forms such as urban canyons and vegetation at the pedestrian level are among the factors affecting the reduction of urban temperatures in urban areas and neighborhoods, the impact of these factors on the outdoor thermal comfort of humans by few research in Iran has been considered. A review of the research background of the subject shows that no serious attention has been paid to the native urban forms of Iran as a factor for reducing urban heat and promoting human health; However, local urban planning helps architects and planners to address urban problems by identifying needs in indoor and outdoor environments to provide the most effective way to reduce the severity of outdoor environments using all design elements. Given that there is still, no place to pay attention to how urban forms change in order to reduce the effects of climate change and outdoor thermal comfort professionally, so the present study focuses on the impact of urban forms on informal settlements and old textures on outdoor thermal comfort. The ambient air temperature and the creation of outdoor thermal comfort in the city of Mashhad, which is one of the cities that experience the most urban forms of informal settlements. The present article, firstly, examines the research done in the thematic field of the article and then in the next part, the theoretical framework is extracted by using articles, dissertations, and books. In the third part of this framework, using simulation in Envi-met software and PET index output in Rayman software and analysis in Leonardo to identify the effects of urban forms on air the temperature in microclimate and outdoor thermal comfort using physiological equivalent temperature index (PET). Studies conducted in the summer and on August 26, 2019, have been selected due to the high heat of the sun and its effect on creating outdoor thermal comfort in open urban spaces.
Materials and Methods,
Due to the nature of the subject, the research method is applied and based on two parts. In the first part, the documentary method is used to formulate the theoretical framework. Thus, by referring to articles, treatises, and books by taking notes, the information needed to understand the thematic literature as well as studies conducted in the field of research has been collected and then using descriptive and analytical methods to prepare and compile the conceptual framework of research. In the next part of the research, the case study was studied and the maps were extracted using GIS. The method of survey and harvesting of climatic information from the Mashhad Climate Organization has been used to collect climatic data. In order to identify the effects of the influential components of the urban form, the Envi-met 4 and Leonardo software collections as well as Rayman have been used. In this study, most simulations were performed in summer (August) and based on data from Mashhad Meteorological Station. This simulation was selected on August 17, 2019, and at sunrise and sunset between 6:00 AM and 8:00 PM local time due to the high temperature of the sun and its effect on ambient temperature and surfaces in open urban spaces. This simulation lasted for 156 hours for three urban forms.
Discussion of Results
The present study investigates the outdoor thermal comfort in informal settlements in Mashhad. Various studies have shown that lowering the ambient temperature in summer can reduce environmental thermal stress and thus improve outdoor thermal comfort. The results in this paper suggest that as the height-to-width (H / W) ratio increases, the sun's access to the environment decreases, and the amount of shading on the surfaces increases resulting in a decrease in ambient temperature. Therefore, it can be said that the height-to-width (H / W) ratio is inversely related to the ambient temperature, and urban form factors such as the height-to-width ratio (H / W) and its shading play an important role in reducing the ambient temperature. On the other hand, the simulations performed to show the temperature difference, so that the difference between the mean indexes (PET) during the hours of thermal stress are 0.68 ° C, 2.53 ° C and 3.27 ° C. The heat stress of the Hojjat fabric is greater than that of the other two fabric and there are more hours in the absence of outdoor thermal comfort, which indicates the temperature difference in all three fabric; but the same the difference stems from different environmental parameters in the three urban forms. One of these parameters is the coverage of outdoor surfaces and materials used in the outer shell of buildings, which is indicated by the Tmrt average temperature index as an important parameter in creating thermal equilibrium in the environment. Studies show that the average temperature index of radiant temperature (Tmrt) is directly related to the PET index and the higher the average temperature index of radiant temperature, the higher the PET index, and vice versa, therefore, the high average radiant temperature in the texture of Hojjat compared to the texture of the agent and the Ghale of the building in the peak hours of heat shows the high rate of heat reflection to the environment in the texture of Hojjat compared to the other two textures. Higher average radiant temperature (Tmrt) in the texture of Hojjat means reflecting more heat than urban levels and can be closely related to the materials used in this texture and the amount of sun access and thus the effect of height to width ratio (H / W) on the ambient temperature. And have levels. Due to the color and texture of the brick, it absorbs less heat and gradually releases the hidden heat and its heat exchange with the environment during the night hours when the air cools down. On the other hand, the temperature a difference of 0.68 C in the first and last hours of simulation in the operating tissue shows that the use of brick materials can reduce the heat exchange with the environment and thus reduce the ambient temperature.