پیش‌بینی تاثیر فضای سبز بر تغییرات خرداقلیمی اماکن مسکونی مشهد طی گرم‌ترین دوره سال

نوع مقاله : مقالات پژوهشی

نویسندگان

1 پژوهشکده علوم گیاهی، دانشگاه فردوسی مشهد

2 دانشگاه فردوسی مشهد

چکیده

با توجه به رشد جمعیت و اقلیم گرم و خشک اکثر شهرهای ایران، تامین و ایجاد آسایش دمایی مناسب در دوره‌های گرم سال ضروری است. به منظور ارزیابی و شبیه‌سازی تاثیر درصد فضای سبز و پوشش گیاهی بر تغییرات دما، رطوبت نسبی و آسایش دمایی شهروندان در دو سایت مسکونی در مشهد، در گرم‌ترین دوره سال 1391 آزمایشی انجام شد. در این آزمایش داده‌های اقلیمی ثبت شده در این دو سایت و داده‌های اندازه‌گیری شده مربوط به سازه‌های شهری و پوشش‌گیاهی با استفاده از برنامه کامپیوتری ان‌وای‌مت مدلسازی و تجزیه و تحلیل شدند. خروجی‌های مدل نشان داد که به‌رغم اختلاف اندک دما و رطوبت نسبی بین سایت‌های واقعی و شبیه‌سازی شده با پوشش گیاهی، تفاوتی از نظر شاخص متوسط نظرسنجی پیش‌بینی شده وجود نداشت و هر دو سایت با وجود پوشش گیاهی شبیه‌سازی شده تا حدود 5/19 درصد، در محدوده تنش گرمایی بسیار شدید قرار داشتند.

کلیدواژه‌ها


عنوان مقاله [English]

Predicting the Impact of Urban Green Areas on Microclimate Changes of Mashhad Residential Areas during the Hottest Period

نویسندگان [English]

  • zahra karimian 1
  • ali tehranifar 2
  • Mohammad Bannayan 2
  • majid azizi 2
  • fatemeh kazmi 2
1 Research Center for Plant Sciences, Ferdowsi University of Mashhad
2 Ferdowsi University of Mashhad
چکیده [English]

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.

کلیدواژه‌ها [English]

  • Relative humidity
  • temperature
  • Thermal Comfort Index
  • vegetation
Afsharkohan J., Balali A. and Ghodsi M. 2012. Investigation of social aspects of problem of urban traffic (Case study: Mashhad). Urban Studies, 4(2): 50-90. (In Persian)
Ali-Toudert F. and Mayer H. 2007. Thermal comfort in an east-west oriented street canyon in Freiburg (Germany) under hot summer conditions. Theoretical and Applied Climatology, 87(1-4): 223-37.
Ali-Toudert, F. 2005. Dependence of outdoor thermal comfort on street design in hot and dry climate, PhD thesis, University of Freiburg, Germany.
Avissar R. 1996. Potential effects of vegetation on urban thermal environment. Atmospheric Environment, 30: 437-448.
Azad R.S. Atmospheric Boundary Layer for Engineers, Kluwer Academic Prees, Dordrecht; 1993. pp. 565.
Cao X., Onishi A., Chen J. and Imura H. 2010. Quantifying the cool island intensity of urban parks using ASTER and IKONOS data. Landscape & Urban Planning, 96(4): 224-31.
Chatzidimitriou A., Chrissomallidou N. and Yannas S. 2005. Microclimate modifications of an urban street in northern Greece. 2005. Proceedings of the PLEA-Passive and Low Energy Architecture. PLEA International, Beirut, Lebanon, pp. 689–694.
Ghahraman A. 2003. Basic Botany, Volume I, Tehran University, Ninth Edition, P. 784. (In Persian)
Gill S.E., Handley J.F., Ennos A.R., Pauleit S., Theuray N. and Lindley S.J. 2008. Characterising the urban environment of UK cities and towns: A template for landscape planning. Landscape and Urban Planning, 87(3): 210-22.
Hardin P.J. 2007. Jensen R.R. The effect of urban leaf area on summertime urban surface kinetic temperatures: a Terre Haute case study. Urban Forestry & Urban Greening, 6: 63-72.
Karimian z. 2014. The Optimizing of Urban Green Space for Thermal Comfort of the Hottest Period of the Year by Modeling Technics Ph.D.: Horticulture sciences, Ferdowsi University of Mashhad, Iran, pp. 198. (In Persian)
Matzarakis A. Climate and bioclimate information for tourism in Greece. Proceedings of the First International Workshop on Climate, Tourism and Recreation. Ed. A. Matzarakis and C. R. de Freitas. International Society of Biometeorology, Commission on Climate Tourism and Recreation; December 2001. WP13, 1-13.
Mauseth J. 1998. Botany: An Introduction to Plant Biology. Jones & Bartlett Publishers; 2nd edition, pp. 837.
McPherson E.G. 1994. Energy-saving potential of trees in Chicago. Chicago's urban forest ecosystem: Results of the Chicago urban forest climate project. USDA forest service, General Technical Report NE, 186: 95-113.
Nagler P., Glenn E., Thompson T. and Huete A. 2004. Leaf area index and normalized difference vegetation index as predictors of canopy characteristics and light interception by riparian species on the Lower Colorado River. Agricultural and Forest Meteorology, 1-17.
National weather service, http://www.weatherbase.com, assessed: 2013/01/01.
Ng E., Chen L., Wang Y., Yuan C. 2011. A study on the cooling effects of greening in a high-density city: An experience from Hong Kong. Building and Environment, 47: 256-71.
Office stabilizes sand and non-desertification. Summary of the National Management Program of deserts (2006-2025), Forest, Rangeland and Watershed Organization; 2006. Tehran. (In Persian)
Pearlmutter D., Kruger E.L. and Berliner P. 2009. The role of evaporation in the energy balance of an open-air scaled urban surface. International Journal of Climatology, 29: 911-20.
Pokorný R. and Stojnič S.2012. Leaf area index of Norway spruce stands in relation to age and defoliation. Beskydy, 5(2): 173–180.
Shaban M., Khajedin S.J., Karimzadeh H. 2007. Iran-Watershed Management Science & Engineering,1(2): 58-63. (In Persian)
Shashua-Bar L., Pearlmutter D. and Erell E. 2011. The influence of trees and grass on outdoor thermal comfort in a hot-arid environment, International Journal of Climatology, 31(10): 1498-506.
Specht R.L. and Specht, A. 2003. Australian plant communities: dynamics of structure, growth and biodiversity, Oxford University Press, South Melbourne.
Streiling S. and Matzarakis A. 2003. Influence of single and small clusters of trees on the bioclimate of a city: a case study. Journal Arboriculture, 29(6): 309–316.
Yin J., He F., Qiu G., He K., Tian J., Zhang W., Xiong Y., Zhao S. and Liu J. 2012. Characteristics of leaf areas of plantations in semiarid hills and gully loess regions. Frontiers of Forestry in China, 4(3):351-357.