نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری، گروه سیستم اطلاعات جغرافیایی و سنجش از دور، دانشکده جغرافیا، دانشگاه تهران، تهران، ایران.
2 دانشیار، گروه سیستم اطلاعات جغرافیایی و سنجش از دور، دانشکدة جغرافیا، دانشگاه تهران، تهران، ایران.
3 دکتری علوم و مهندسی آب، معاونت آب و خاک وزارت جهاد کشاورزی، کرج، ایران.
چکیده
گسترش فیزیکی شهری بر تغییرات مکانی و زمانی در خواص بیوفیزیکی سطح (از جمله دمای سطح زمین) تأثیرگذار بوده و منجر به افزایش دمای سطح طی سالهای پایش شده است. به طوری که نتایج حاصله در هر سه شهر مورد مطالعه طی سالهای پایش، روند افزایشی دمای سطح زمین را نشان میدهد. بررسیها در شهرها نشان داد که رشد شهری با توجه به محیط جغرافیایی و شرایط طبیعی هر منطقه از الگوهای متفاوتی پیروی میکند. برایناساس، تغییرات مکانی و زمانی در خواص بیوفیزیکی سطح در میان شهرهای انتخاب شده متفاوت بود. این تفاوت ناشی از شرایط اقلیمی، محیطی و پوشش زمین بود. با توجه به شرایط اقلیمی، میانگین سرسبزی در مناطق با هوای مرطوب (بندر انزلی و شیرگاه) با مناطق با هوای گرم و خشک (کاشان) متفاوت بود. با کاهش پوشش گیاهی سطح، میزان تبخیر و تعرق سطحی کاهش یافته و در نتیجه گرما و خشکی سطح افزایش مییابد. میزان سبزینگی در هر سه شهر مورد مطالعه طی سالهای پایش، روند کاهشی داشته که میتواند به دلیل پدیده گسترش شهری باشد. نتایج حاصل از شاخص درخشندگی نشان داد در شهرهای مرطوب یعنی بندرانزلی و شیرگاه میزان درخشندگی که ناشی از عوارض شهری بوده، روند افزایشی داشته است. نتایج حاصل از شاخص آب و رطوبت نیز طی سالهای پایش در شهرهای شیرگاه و بندر انزلی(شهرهای مرطوب) روند افزایشی داشته است. بهطور کلی با کاهش سبزینگی، درخشندگی، رطوبت و دمای سطح زمین در شهرهای کاشان و شیرگاه افزایش یافته ولی به نظر میرسد تأثیر اقلیم محلی و دریا منجر به تعدیل دما در بندر انزلی شده است. نزدیکی به دریا و بالابودن رطوبت باعث شده پوشش گیاهی در طی سالهای پایش کاهش چشمگیری نداشته باشد و در نتیجه منجر به تعدیل دمای سطح شده و از سال ۱۹۹۱ تا ۲۰۲۱ نتایج مربوط به LST تنها یک درجه افزایش دما را نشان میدهد. درنتیجه افزایش پوشش گیاهی میتواند منجر به افزایش رطوبت آب و در نتیجه کاهش دمای سطح شود.
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
The Effect of Climatic Conditions on Spatio-Temporal Changes and biophysical Characteristics of cities Using Satellite Images (Case study: Kashan, Shirgah, Bandar Anzali cities, Iran)
نویسندگان [English]
- Bahare sadat mousavi 1
- Ata Abdollahi kakroodi 2
- samane Arvandi 3
1 Department of Geographical Information System and Remote Sensing, Faculty of Geography, University of Tehran, Teharn.Iran.
2 Department of Geographical Information System and Remote Sensing, Faculty of Geography, University of Tehran, Teharn.Iran.
3 Ministry of Agriculture-Jahad, Deputy of water and soil, Karaj, Iran.
چکیده [English]
Highlights
- Urban physical expansion has had an impact on spatial and temporal changes in Tasseled cap, including Land Surface Temperature (LST), resulting in an increase in surface temperature.
- Surveys conducted in cities have shown that the patterns of urban expansion are influenced by the geographic setting and regional factors.
- The average greenness in areas with wet weather conditions (such as Bandar Anzali and Shirgah) differs from areas with hot and dry weather conditions (such as Kashan), based on climatic conditions.
Introduction
Globally, the physical growth of cities is recognized as a major threat to natural and ecological resources, with a variety of effects including land use change, increased pollution, increased earth surface temperatures, and climate change in both urban and non-urban areas. Planning to minimize the negative environmental effects of urban growth can be aided by quantifying and monitoring the changes caused by urban development in the Tasseled cap of the surface. Urban management and planning can also be derived from the quantitative and qualitative effects of climatic conditions on the type and amount of changes in the Tasseled cap of the surface due to physical expansion of the cities. Furthermore, weather conditions are the primary and effective factor on the type and amount of changes in the Tasseled cap properties of the surface. Considering field measurement is a time-consuming and expensive technique, remote sensing technology will be helpful and effective to overcome this challenge because of its large and continuous coverage, immediate access, and availability of data at various local, regional, and global scales.
Theoretical Framework
Urbanization leads to an increase in land surface temperature (LST). In general, at the patch scale, the more compact the urban growth, the more easily the surface warmed. In most temperature zones, it was found that edge expansion and infilling had significant and favorable correlations with LST. Positive correlations were found in the warm temperature and plateau climatic zones, while negative correlations were seen in the subtropical and intermediate temperature zones, indicating that the influence of outliers on LST had opposite effects in these regions. The findings also demonstrated that LST was significantly influenced in diverse ways by patch area, industrial firm density, population density, and road density. This study further verified the existence of a scale effect; moreover, the results of patch-scale research based on the microscopic perspective were deemed to be more accurate. Overall, understanding the quantitative relationships between UGP and LST is helpful for assessing the complexity of urban climates and for providing a scientific basis for planners and urban managers to optimize urban layouts, (Rao et al., 2021: 105314).
Methodology
The physical development of cities and their impact on the surface's Tasseled cap have been the subject of numerous studies. This research was conducted with the aim of investigating the effect of different climatic conditions on the changes in Tasseled cap by using remote sensing. The cities of Kashan, Bandar Anzali, and Sirjan were chosen as the study regions for this research because of their diversity in geographical features, climatic features, and land cover. So, between 1991 and 2021, the effects of various climatic conditions and changes in thermal temperature on these cities were examined. For this purpose, satellite images of Landsat 5 TM sensor and Landsat 8 OLI sensor used.
Conclusion
This study investigated the effect of climatic conditions on the spatial and temporal changes in Tasseled cap, including LST, in three cities in Iran: Kashan, Sirjan, and Bandar Anzali. The results showed that urban expansion has led to an increase in LST in all three cities. However, the increase in LST was more pronounced in Kashan, which has a hot and dry climate, than in Sirjan and Bandar Anzali, which have more humid climates. This is because the reduction of vegetation cover in urban areas reduces evaporation and transpiration, which leads to an increase in surface temperature.
The study also found that the changes in other Tasseled cap indices, such as brightness and wetness, were also affected by climatic conditions. In the humid cities of Bandar Anzali and Sirjan, the increase in LST was accompanied by an increase in brightness and wetness. This is because the presence of vegetation helps to reflect sunlight and retain moisture, which helps to cool the surface. In contrast, in the hot and dry city of Kashan, the increase in LST was accompanied by a decrease in brightness and wetness.
The findings of this study suggest that the planning and management of urban areas should take into account the local climatic conditions. In hot and dry climates, it is important to preserve vegetation cover to help reduce surface temperatures. In humid climates, it is important to design urban spaces in a way that maximizes the benefits of vegetation, such as shading and moisture retention.
The study also suggests that future studies should consider the effects of climatic conditions on the changes in Tasseled cap in different cities. This will help to improve our understanding of the relationship between urban development and climate change.
کلیدواژه‌ها [English]
- Urban development
- spatio-temporal variations
- land surface temperature
- and Tasseled cap properties
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