نوع مقاله : مقاله پژوهشی

نویسندگان

گروه منابع طبیعی و محیط زیست، دانشکده فنی و مهندسی، واحد بوشهر، دانشگاه آزاد اسلامی، بوشهر، ایران

چکیده

سابقه و هدف:
افزایش سطوح غیر قابل نفوذ بهدلیل شهرنشینی، اثرهای نامطلوب بسیاری بر سیستمهای اکولوژیک شهری، از جمله خطرهای محیط زیستی ناشی از گرمای محیط شهری ایجاد کرده است. تعیین رابطه بین ترکیب کاربری و پوشش زمینها و دمای سطح زمین (LST) ، میتواند تأثیر قابل ملاحظه ای بر کاهش دما در محیط های شهر داشته باشد. در سالهای اخیر، گسترش شهر بوشهر موجب  افزایش سطوح غیر قابل نفوذ، تغییر فضای سبز و تغییر قابل توجه محیط زیست شهری شده است. بنابراین، بررسی تأثیر فضاهای سبز بر محیط پیرامونی در برنامه ریزی شهر بوشهر ضروری است.
مواد و روشها:
به منظور آشکارسازی اثرهای فضای سبز در محیط های حرارتی شهری، در این تحقیق از تکنولوژی سنجش از دور برای استخراج فضاهای سبز، دمای سطح زمین و پوشش زمین از تصاویر لندست OLI( مرداد 1397 )بدون پوشش ابری از آرشیو دادههای (USGS) لندست، استفاده شد. مشاهده های میدانی در ماه مرداد سال 1397 انجام شد و تغییرات دما و رطوبت نسبی در محیط پیرامونی 13 محدوده فضای سبز شهر بوشهر اندازه گیری و ثبت شد. برای تجزیه و تحلیل داده های حاصل از اندازه گیری میدانی، مدل رگرسیون خطی چند متغیره بین دما و رطوبت نسبی با سه متغیر جهت، فاصله و اندازه فضاهای سبز تعیین شده و آثار متقابل بین متغیرها بررسی شد. با اجرای مدل رگرسیون چند متغیره، رابطه بین داده های دما و رطوبت نسبی مربوط به هر نقطه محاسبه شد. آزمون توکی بین میانگین های تغییرهای دمایی و رطوبت نسبی مربوط به هر یک از سه متغیر در سطح اطمینان 95 %انجام شد. 
نتایج و بحث:
نتایج ضریب تبین R 2محاسبه شده از مدل رگرسیون خطی بین سنجه نرمال شده تفاوت پوشش گیاهی (NDVI)  با دمای سطح زمین برابر با 0.72 نشان دهنده وابستگی باال بین تغییرهای دما با تغییرات NDVI است. نتایج حاصل از تحلیل تغییرهای دما با تغییر NDVI نشان داد که تغییرات NDVI که در واقع سنجه فراوانی گیاه است از عاملهای بسیار مهم در کاهش دما و یا در بهبود و افزایش مهمترین کارکرد اکولوژیکی فضای سبز شهری است. نتایج حاصل از دادههای ثبت شده در فاصلهها و جهتهای متفاوت از فضاهای سبز، نشان دهنده کاهش تدریجی دما و افزایش رطوبت نسبی با کاهش فاصله از محدوده های منتخب بوده است. بر این اساس، میزان تأثیر فضاهای سبز بر دما و رطوبت نسبی، تا فاصله 60 متر معنی دار به دست آمد (  p≤0.05 ) همچنین، جهت جغرافیایی غربی دارای کمترین R 2 میزان دما و بیشترین رطوبت نسبی و جهت جغرافیایی شرقی دارای بیشترین میزان دما و کمترین رطوبت نسبی بوده است. میزان بهدست آمده از مدل خطی بین دما و رطوبت نسبی با روابط متقابل بین سه متغیر (جهت، فاصله و اندازه فضاهای سبز) نیز بهترتیب برابر با 0.88 و 0.99 بوده است.
نتیجه گیری:
نتایج به دست آمده نشان داد که فضای سبز شهری نقش مهمی در بهبود محیط حرارتی شهری دارد. با استفاده از تکنولوژی سنجش از دور و مقایسۀ محیط حرارتی، میتوان گفت موقعیت و فاصله مکانی از فضاهای سبز شهری بر الگوی حرارتی در محیط شهری تأثیر میگذارد. ما می توانیم قوانین ویژه ای را برای توزیع فضاهای شهری و دامنه های خنک کننده در فصل های گرم در محیط پیرامونی فضاهای سبز شهری داشته باشیم

کلیدواژه‌ها

عنوان مقاله [English]

The influence of green spaces on land surface temperature and humidity of the surrounding environment in Bushehr city

نویسندگان [English]

  • Fazel Amiri
  • Tayebeh Tabatabaie

Department of Natural Resources and Environment, Faculty of Engineering, Islamic Azad University, Bushehr Branch, Bushehr, Iran

چکیده [English]

Introduction:
The increase in impervious surfaces due to the urbanization has caused many adverse effects on urban ecological systems, including the urban heat environmental risk. Revealing the relationship between land use/land cover composition and land surface temperature (LST) gives insight into how to effectively reduce the temperature in urban environments. In recent years, the expansion of Bushehr city has resulted in an increase in impervious surface, the decrease of green space and a significant change in the temperature. It is also essential to determine the influence of green spaces on the surrounding environment in urban planning of Bushehr.
Material and methods:
In order to reveal the comprehensive effects of green space on the urban thermal environment in the severely hot regions, this paper adopts remote sensing technology to extract and analyze green space, land surface temperature (LST), and land cover (LC) from the Landsat spectral imaging data (August 2018) with clear-sky conditions. A field survey was carried out in August 2018 and temperature and relative humidity was recorded for 13 selected green spaces in the Bushehr city. To analyze the field data, a multivariate linear regression model between temperature and relative humidity with three variables of direction, distance, and the size of green spaces was determined and interactions between variables were investigated. By applying a multivariate regression model, the relationship between temperature and relative humidity data was calculated for each point. Tukey test was carried out between the averages of temperature variations and relative humidity for each of the three variables at a 95% confidence level.
Results and discussion:
The results of the R2 correlation coefficient from the linear regression model between normalized difference vegetation index (NDVI) and land surface temperature equal to 0.72 indicated a high correlation between temperature and NDVI variations. The results of the temperature variation analysis with NDVI changes indicated that NDVI variations, which are actually plant frequency indices, were one of the most important factors in reducing temperature or in improving the most important ecological function of urban green space. The results of the recorded data at different intervals and directions from the green spaces indicated a gradual decrease in temperature and an increase in relative humidity by reducing the distance from the green spaces. Accordingly, the effect of green spaces on temperature and relative humidity was significant up to a distance of 60 meters (p≤0.05). The western direction had the lowest temperature and the highest relative humidity and the eastern direction had the highest temperature and the lowest relative humidity. The R2 correlation coefficient obtained from the linear model between temperature and relative humidity with the interactions between the three variables (direction, distance, and the size of green spaces) were also 0.88 and 0.95, respectively.
Conclusion:
The results indicated that urban green space plays a significant role in improving the urban thermal environment. By using remote sensing technology and comparing the thermal environments, we conclude that the location and distance of urban green spaces affect the thermal pattern in an urban environment. We can establish certain rules on the distribution of the urban green space and the cooling ranges in hot seasons in the surroundings of urban green spaces

کلیدواژه‌ها [English]

  • Urban green spaces
  • land surface temperature (LST)
  • Land cover (LC)
  • Landsat image
  • Bushehr

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