چکیده:
جهان امروزه جریان بیسابقهای از شهری شدن را تجربه مینماید. رشد جمعیت و توسعه شهرنشینی موجب تغییرات کاربری اراضی در نواحی شهری شده است. یکی از پیامدهای این تغییرات، افزایش دمای سطح زمین در نواحی شهری و شکلگیری جزیره گرمایی میباشد هدف اصلی از این تحقیق پایش دمای سطح زمین و رابطهای آن با پوشش اراضی میباشد. به همین منظور ابتدا تصاویر ماهواره لندست 8 و 7، اخذ شد. سپس با استفاده از روش طبقهبندی نظارت شده - الگوریتم حداکثر احتمال، نقشه پوشش اراضی به سه طبقه اراضی انسانساخت، بایر و پوشش گیاهی طبقهبندی گردید و درنهایت بهمنظور پایش دمای سطح زمین، نقشه دمای سطحی شهر کاشان با استفاده از الگوریتم تککاناله استخراج گردید. تحلیل پوشش اراضی نشان داد که اراضی انسانساخت طی سالهای 1385 تا 1400 با رشد 05/21 درصدی، روند افزایشی داشته است و اراضی بایر و اراضی دارای پوشش گیاهی (به ترتیب با 17/11 درصد و 88/9 درصد) روند کاهشی داشته است. حداقل دمای سطح زمین در سال های 1385 و 1400 به ترتیب از87/34سانتیگراد به 33/42 درجه سانتیگراد رسیده است. همچنین در این مدت، حداکثر دما از63/59 درجه سانتیگراد به 70/60 درجه سانتیگراد افزایشیافته است. پوششهای گیاهی در سالهای موردمطالعه کمترین دمای سطحی را به خود اختصاص دادهاند. شهر کاشان باتوجهبه ماهیت اقلیمی و مکانی خود، همچون دیگر مناطق خشک و نیمهخشک ایران، دارای دمای سطحی کمتری نسبت به محیط اطراف خود میباشد، این پدیده با عنوان جزایر خنک شهری شناخته میشود. تحلیل خودهمبستگی فضایی موران در سطح اطمینان 99 درصد نشان داد که دادههای دمای سطحی شهر کاشان به شکل خوشهای توزیع شدهاند. بر اساس شاخص Gi*، در تمامی سالهای موردمطالعه، دمای حداکثر متعلق به زمینهای بایر بوده است.
The world is experiencing an unprecedented flow of urbanization. Population growth and urbanization have changed land use in urban areas. One of the consequences of these changes is the increase in the temperature of the earth's surface in urban areas and the formation of a heat island. The main purpose of this research is to monitor the surface temperature of the earth and its relationship with land cover. For this purpose, Landsat 8 and 7 satellite images were taken first. Then, using the supervised classification method - maximum likelihood algorithm, the land cover map was classified into three classes of man-made land, barren land and vegetation and finally, in order to monitor the surface temperature of the earth, the surface temperature map of Kashan city was extracted using single channel algorithm. The analysis of land cover showed that man-made lands increased by 21.05 percent during the years 1385 to 1400, and barren lands and lands with vegetation (with 11.17 percent and 9.88 percent, respectively) has had a decreasing trend. The minimum temperature of the earth's surface has reached from 34.87 degrees Celsius to 42.33 degrees Celsius in 1385 and 1400, respectively. Also, during the 15-year period, the maximum temperature has increased from 59.63 degrees Celsius to 60.70 degrees Celsius. Vegetation has the lowest surface temperature in the studied years. Due to its climatic and spatial nature, the city of Kashan, like other arid and semi-arid regions of Iran, has a lower surface temperature than its surrounding environment, this phenomenon is known as urban cool islands. Moran's spatial autocorrelation analysis at the 99% confidence level showed that the surface temperature data of Kashan city are distributed in clusters. According to the Gi* index, in all the studied years, the maximum temperature belongs to barren lands. Extended Abstract 1-Introduction The rapid development of cities has had negative effects on the quality of the global environment due to extensive changes in land use and land cover. The change of land cover and land use and the development of urban and agricultural areas and deforestation have changed the regional and local temperature regime. Knowing the Earth's surface temperature significantly contributes to a wide range of geoscience issues such as urban climate, global environmental change, and the study of human-environment interaction. Therefore, investigating the relationship between land cover changes and land surface temperature (LST) is one of the important parameters in urban-regional planning, and it is necessary to plan a new and successful method to achieve better urbanization and reduce environmental effects on cities. A city should be introduced according to the spatial distribution of land surface temperature (LST). 2-Materials and Methods In this study the effect of land use and land cover changes on the formation of hot and cold islands was investigated. In order to investigate the effect of different land covers in the study area on land surface temperature and land use changes over a 15-year period, images were first prepared from the website of the United States Geological Survey (www.usgs.gov). Then, using ENVI 5.3 software, pre-processing operations were performed to apply atmospheric and radiometric corrections, and using the supervised classification method and the maximum likelihood algorithm, the land cover was divided into three categories: man-made, vegetation and bare land. Then, in order to understand the effect of land cover changes on the spatial distribution of urban cool islands, the ground surface temperature was calculated using a single-channel algorithm. The satellite images of Landsat 7 and 8 sensors have been used in the period of 2006 and 2021 to check the land surface temperature of urban area. The image of Landsat 8 satellite was used to extract the land cover map from OLI sensor and TIRS1 sensor. The Landsat ETM+ sensor image was used to extract the land surface temperature and also to prepare the land cover map using visible and infrared bands to extract the land surface temperature. In order to investigate autocorrelation and spatial clustering, hot spot pattern, Moran's I and Getis-Ord GI were used. 3- Results and Discussion The survey of land cover changes during the 15-year period from 2006 to 2021 shows that about 21percent has been added to the built-up area of the city. Following this increase, the extent of barren land and vegetation land has decreased by about 12 percent and 10 percent, respectively. Considering the influence of the land surface temperature on the land cover of urban areas, changes in the land cover in urban areas will cause temperature changes. The results of the study show that barren lands had the highest average temperatures (52.11 and 55.57 degrees Celsius) in both research periods. Also, the results show that during the 15-year period, the vegetation lands have the lowest average surface temperature with 46.21 and 49.62 degrees Celsius. In the areas where the change of land cover from barren and man-made lands to vegetation land has occurred, due to the effect of the greenness index on the temperature of the land surface due to the simultaneous creation of shade and humidity. In these conditions we see a decrease in temperature between 4 and 5 degrees Celsius. During the studied period, after barren lands, man-made lands had the highest temperature with an average temperature of 50.48 in 2006 and 50.34 degrees in 2021. During the day, the land surface temperature in the city center is lower than in the suburbs, and in the parts of the city center, we see urban cool islands. The outcomes of two considered spatial statistics indicated the clustering, pattern for LST of the Kashan city. In addition, there was a good agreement between the results of Getis-Ord GI statistic (hot spots spatial analysis) and the Local Moran's I statistic (spatial autocorrelation) on the spatial pattern of heat and cool clusters. 4- Conclusion The results of the research show that the highest temperature of the land surface in the two studied periods is related to barren lands and the lowest surface temperature belongs to vegetation land. According to the effect of land surface temperature on the land cover of urban areas, based on the results, it can be said that there is a significant relationship between the temperature and the land cover of the region. The pattern of spatial changes in the surface temperature of Kashan city is mostly related to the pattern of spatial changes of vegetation cover and barren lands. Spatial autocorrelation analysis with local Moran indices showed that the land surface temperature in Kashan city has a spatial structure; In other words, high and low temperature cells tend to concentrate or cluster in space. Analysis of hot spots has been a clear confirmation of the clustering of cool urban islands (99% confidence level) at the man-made areas. The results of the research show the importance of planning, managing and preserving areas with vegetation and preventing them from turning into built-up and barren lands in order to maintain the environmental sustainability of urban areas.
خلاصه ماشینی:
در پژوهشي ترائوره و همکاران 1- Land Surface Temperature 2- Urban Heat Island (٢٠٢١) به ارزيابي تغييرات کاربري /پوشش زمين و اثرات آن بر دماي سطح زمين در بانگوي (پايتخت جمهوري آفريقاي مرکزي ) اقدام نموده اند.
نتايج اين مطالعه نشان مي دهد به موازات تغييرات کاربري اراضي، بين سال هاي ١٩٨٦ تا ٢٠١٧، ميانگين دماي سطح زمين در شهر افزايش يافته است (٢٠٢١ ,.
محدوده شهر کاشان و تراکم در سطح نواحي داده هاي مورداستفاده و روش مطالعه به منظور بررسي ميزان توسعه مکان هاي گرم شهر و مشخص نمودن الگوهاي حرارتي شهري ، تصاوير ماهواره اي سنجنده هاي لندست ٧ و ٨، در بازه زماني ٢٠٠٦ و ٢٠٢١ ميلادي استفاده شده است .
اطلاعات تصاوير سنجنده لندست ٧ و ٨ منبع : متاديتا تصاوير اطلاعات تصاوير مربوط به سال ٢٠٠٦،٢٠٢١ ماهواره لندست (محدوده شهر کاشان ) نوع سنجنده ستون سطر درصد پوشش ابر زاويه خورشيد زمان گرينويچ تاريخ لندست -٨ ١٦٤ ٣٦ ٠/٠٩ ١١٨/٩٢٢٣٦٩٧٠ ٠٧:٠٨:٢٧ ٢٠٢١/٠٧/٢٠ لندست -٧ ١٦٤ ٣٦ ٠٠٠ ١١٤/٨٢٨٨١٠٨٨ ٠٦:٥٨:١٥ ٢٠٠٦/٠٧/١٩ نقشه پوشش اراضي در اين پژوهش ، براي بررسي، اثر پوشش اراضي مختلف منطقه موردمطالعه بر روي دماي سطح و تغييرات کاربري اراضي در طي دوره ي زماني ١٥ساله ، ابتدا تصاوير از وب گاه سازمان زمين شناسي ايالات متحده آمريکا ٢ تهيه شد.
نتيجه گيري مطالعه حاضر باهدف بررسي رابطه بين پوشش اراضي و دماي سطح زمين در شهر کاشان با استفاده داده هاي سنجش ازدور انجام شد.