zahra karimian; Ali Tehranifar; Mohammad Bannayan; Majid Azizi; Fatemeh Kazemi
Abstract
Introduction: Considering population growth and urbanization development, one of the main requirements of the urban society is to create appropriate life condition for dwellers. The microclimate is considered as one of the factors that affect the activity of people in the environment and in terms of ...
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Introduction: Considering population growth and urbanization development, one of the main requirements of the urban society is to create appropriate life condition for dwellers. The microclimate is considered as one of the factors that affect the activity of people in the environment and in terms of tourist and recreational industry, it is considered as an important source of economic. Many climatic parameters such as temperature, relative humidity, radiation and wind speed can affect the quality of people's recreational activities. So far, many studies have been conducted in the world about the positive effects of vegetation specially trees in the urban landscape on the optimizing of microclimate and human thermal comfort. The cooling mechanism of trees and clouds in an area mainly by directly shading the ground surface and indirectly by supplying humidity are similar. Thus, perhaps it be possible to calculate the changes in temperature and relative humidity based on cloud categories and impute it to tree canopy and vegetation size. The purpose of the present study was to answer followed questions, 1) does the use of single tree produce a sensible difference in temperature and humidity relative to open space? 2) Does the acacia tree as an indicator for a broad-leaved species compare to the pine tree as an indicator for the needle species in terms of the microclimatic variation of around themselves act differently? 3) Do the microclimatic elements (Temperature and relative humidity) under the canopies are comparable to various cloudiness conditions?
Materials and Methods: The experiments were conducted at Ferdowsi University of Mashhad. The climate data under two species of false acacia (Robinia pseudoacacia) and pine trees (Pinus eldarica) and open space were received from Mashhad weather station over a period of 19 years, recorded and analyzed. In the comparison of the effects of vegetation and cloudy conditions on the temperature and relative humidity an assumption was proposed that has been mentioned in the following. The differences between the means of temperature and relative humidity obtained under SKC (Sky Clear) cloudiness conditions and in open space; under SCT (Scattered Sky) conditions and pine trees; and under BKN (Broken Sky) conditions and false acacia tree must be equal or these differences must be statistically not significant. In addition to the effect of tree canopy, the effects of days and hours on the temperature and humidity were investigated. To analysis and also mean comparison, SPSS 16 software was used.
Results and Discussion: The results showed that the temperature (decreasing) and relative humidity (increasing) were significantly different among various cloudiness conditions during 19 years. The results also indicated that between the temperatures recorded under the canopy of pine and false acacia trees, and also among of recorded relative humidity in two trees specious with corresponding outdoor spaces there were significant differences. Also, there were no significant differences among the temperature of the clear sky and the partly cloudy with that of the mostly cloudy sky. Further, clear sky and mostly cloudy sky showed significant differences in terms of relative humidity. Mostly cloudy sky and the partly cloudy sky compared with pine and false acacia trees were about 4.6 and 4.5oC cooler, respectively. The cloud covers, also could enhance the more level of relative humidity in the environment in comparison with single tree canopy, so that were caused a wetter environment equal to16.6 and 8.4 percent, respectively. The results also showed that temperature and relative humidity created by the shade from false acacia and pine trees are not comparable with the same climatic factors created by partly cloudy and mostly cloudy skies. In the present study, false acacia as a broad-leaved tree compared with pine tree and also open space could cool the environment about 0.65 degree C more that is in line with previous studies that showed the microclimatic impact of vegetation depend on crown and leaf size. Temperature and relative humidity in vegetation (trees) and cloudy condition are not comparable with microclimate and their impact on the environment is not the same. The cloud covers, also could enhance the more level of relative humidity in the environment in comparison with single tree canopy, so that were caused a wetter environment equal to16.6 and 8.4 percent, respectively.
Conclusion: This finding showed that climatic effects of cloud covers had no similarity compared with two studied trees species. It may also indicate that green space and greenery should not also be ignored in areas where cloudy skies are mostly present throughout the year.
zahra karimian; ali tehranifar; Mohammad Bannayan; majid azizi; fatemeh kazmi
Abstract
Introduction: With regard to two adverse climatic phenomena of urban heat islands and global warming that has been leading to increase temperature in many cities in the world, providing human thermal comfort especially in large cities with hot and dry climates, during the hottest periods of the year ...
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Introduction: With regard to two adverse climatic phenomena of urban heat islands and global warming that has been leading to increase temperature in many cities in the world, providing human thermal comfort especially in large cities with hot and dry climates, during the hottest periods of the year is crucial. Mainly vegetation with three methods: shading, evapotranspiration and wind breaking can affect micro-climate. The aim of this study was to asses and simulate the impact of existing and proposed vegetation on the human thermal comfort and micro climate changes in some residential areas of Mashhad during the hottest periods of the year by using a modeling and computer simulation approach.
Materials and Methods: This research was performed in the Ghasemabad residential area, Andisheh and Hesabi blocks, and in the hottest period of the year 2012 in Mashhad. Recorded data in the residential sites along with observed data from Mashhad weather station that included temperature, relative humidity, wind speed and direction. Soil data (soil temperature and humidity, soil\ type), plant data (plant type, plant height, leaf area index) and building data (inner temperature in the building, height and area buildings) as input data were used in the ENVI-met model. Both two sites, Andishe and Hesabi residential blocks, with vegetation (different trees and bushes plants, for example Acacia, ash, sycamore, mulberry, chinaberry, barberry, boxwood and Cotoneaster that all of them are tolerant and semi-tolerant to drought) about 20% were simulated. Regarding the area of simulating, 3 receptors were considered in per sites. Simulation was commenced from 6 AM and continued until 18 pm, but just data of 11-15 hours were analysed (the hours of peak traffic).
Results and Discussion: Analysis of outputs data revealed that the temperature of two residential sites in all three receptors during the study were almost the same. In general, the maximum temperature difference between receptors was obtained at 13 hour. The trend of relative humidity changes was very similar in both residential sites. In these two sites the most differences in the relative humidity was obtained at 12 oclock.. In addition, the trend of Predicted Mean Vote (PMV) in Andisheh residential block showed that these changes in central and south-west part of the site were similar. The simulation with vegetation in the sites, also, showed that the trend of temperature and relative humidity changes were similar. The trends of temperature changes in residential site, Hesabi, in the defined receptors were very similar. So that temperature increased from 12 oclock to 15. While the trend of relative humidity changes was quite the reverse. This study results showed that the difference in temperature, relative humidity and PMV between measured and simulated data were minimal in both residential sites. Moreover, the data comparison of PMV indicated that in both residential sites, despite of simulation with vegetation, the human thermal comfort did not improve, so that these sites were in the range of extreme heat stress. There are several reasons to justify this issue, such as the percentage and the type of vegetation, factors related to the topography and geography of area, building distribution and density, type and color of the building materials and surfaces, etc. However, in this part of the study, other factors were constant, except vegetation. It seems that with increase of percentage and the ratio of vegetation, changes in temperature, relative humidity and other micro-climate factors, are created, but sometimes for the reasons stated, the temperature during the hottest period of the year is too high so that increase in vegetation will have little impact on outdoor thermal comfort. It might be the simulated area on these sites as well as the type and the ratio of the selected species to reduce the temperature and increase the relative humidity have been not adequately represent all conditions which be able to improve thermal comfort.
Conclusions: In this study eventually we can conclude that in the simulated sites with about 20 percent vegetation cover,, despite the slight decrease and increase in temperature and relative humidity, respectively compared with the real sites, the thermal comfort range was similar. It is advisable in the future studies to simulate the green area in shape of the vertical and horizontal, changes in species composition in green area like trees, shrubs, and cover plants and also the test of different combinations of type and percentage of vegetation.
Tahereh Bahrami; Vahid rouhi; abdolrahman mohammadkhani; saeid reezi
Abstract
Introduction: Green roof is one of the newest phenomenons in architecture and urbanism that refers to the sustainable development concepts and it will be usable for increasing landscape design, improving quality of the environment and reduction in energy consumption. Ensure of existing adequate green ...
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Introduction: Green roof is one of the newest phenomenons in architecture and urbanism that refers to the sustainable development concepts and it will be usable for increasing landscape design, improving quality of the environment and reduction in energy consumption. Ensure of existing adequate green landscape in urban areas and improving access to natural areas surrounding the cities can help to offset negative effects of urban life. The use of green roof technology in cities is one of advanced techniques of green landscape. A green or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium on top view of buildings. Green roof layers that considered for roof side consist of protection layer, drainage layer, growing medium and plant layer. Medium layer is the medium culture of green roof that plants are begins to grow in it. This space should enable to save enough minerals and water for conserve of green-roof plants. All kinds of plants can growth on the green roof, but there are some constraints in creative of design because of roots dimension, plant canopy, necessary volume of soil, suitable direction to light, good weather, weight of designed structures, budget of repairing and keeping.
Materials and Methods: To evaluate the effect of some culture medium on water consumption, vegetative and reproductive traits of Gazania (Gazania hybrida) in condition of green roof a factorial experiment was conducted based on a completely randomized design with nine treatments and three replications in 2014. Treatments were three levels of vermicompost (zero, 5%, and 10%) and rice hull (zero, 7, and 14%). Seedlings of plants cultivated in the media mixture of coco peat 15%, perlite 15%, leaf 10%, manure 10%, and filed soil 50%. The container had 60 × 60 ×25 cm dimensions that placed on the roof of greenhouse building with four meters height. The measured traits was number, average, and diameter of flower, stem diameter, plant height and diameter, crown diameter, the number of produced seedlings, root volume and chlorophyll. The weight of different mediums measured for medium of green roof suitable texture. In addition, in the certain period (three months), water consumption calculated with considering of daily evaporate and transpiration for each of medium. Data analyzed using SAS and MSTAT-C statistical program and means compared using a Duncan test (p < 0.05).
Results and Discussion: The results showed that vermicompost treatments had significant effects on the number and diameter of flowers and stem height of the plant, but had no effect on plant's stem diameter. Based on the results, different amounts of vermicompost increased the flower number and average per day and also the plant length. The largest flower number (88.33) and average (6.3) per day and the plant length (14.52) were observed in 10% vermicompost treatment and the lowest observed in control treatment. In addition, rice hull treatments had significant effect on flower number and diameter. However, rich hull had not any significant effect on stem number and diameter. Mean comparisons showed the highest and lowest flower number (82.4 and 82.1), mean flower number per day (5.88 and 5.86) in 14% and 7% rice hull treatments, respectively. Also, the highest flower diameter was related to 14% rice hull treatments. Result of analysis variance table showed significant effect on flower crown weight, length and diameter and root volume. Rice hull treatments also had significant effect on flower crown number and diameter and root volume. In this study, combination of 10% vermicompost with %7 rice hull treatment, have the greatest impact on the latedmost traits and reducing water consumption on green roof. As results showed water consumption in the certain period (three months), the lowest consumption belonged to 14% rice hull without vermicompost that had lowest water consumption in comparison with reference. In addition, the heaviest weight of different mediums was related to control and the lightest medium was belonged to 5%, vermicompost in combination with 14% rice hull.
Conclusion: The vermicompost and rice hull as bio-fertilizers not only increased structure, physical and chemical condition of medium but also increased nutrition and reduced water consumption. Vermicompost and rice hull both improved the most flower traits on green roof and reduced water consumption and weight of different mediums. Therefore, the vermicompost and rice hull (14% and 7%) combined with soil mixture can be used as a culture medium in green roofs.
