Designing “liveable” cities as climate change effects are felt all over the world has become a priority to city authorities as ways are sought to reduce rising temperatures in urban areas. Urban Heat Island (UHI) ef...Designing “liveable” cities as climate change effects are felt all over the world has become a priority to city authorities as ways are sought to reduce rising temperatures in urban areas. Urban Heat Island (UHI) effect occurs when there is a difference in temperature between rural and urban areas. In urban areas, impervious surfaces absorb heat during the day and release it at night, making urban areas warmer compared to rural areas which cool faster at night. This Urban Heat Island effect is particularly noticeable at night. Noticeable negative effects of Urban Heat Islands include health problems, air pollution, water shortages and higher energy requirements. The main objective of this research paper was to analyze the spatial and temporal relationship between Land Surface Temperature (LST) and Normalized Density Vegetation Index (NDVI) and Built-Up Density Index (BDI) in Upper-Hill, Nairobi Kenya. The changes in land cover would be represented by analyzing the two indices NDVI and BDI. Results showed the greatest increase in temperature within Upper-Hill of up to 3.96°C between the years 2015 and 2017. There was also an increase in impervious surfaces as indicated by NDVI and BDI within Upper-Hill and its surroundings. The linear regression results showed a negative correlation between LST and NDVI and a positive correlation with BDI, which is a better predictor of Land Surface Temperature than NDVI. Data sets were analyzed from Landsat imagery for the periods 1987, 2002, 2015 and 2017 to determine changes in land surface temperatures over a 30 year period and it’s relation to land cover changes using indices. Visual comparisons between Temperature differences between the years revealed that temperatures decreased around the urban areas. Minimum and maximum temperatures showed an increase of 1.6°C and 3.65°C respectively between 1987 and 2017. The comparisons between LST, NDVI and BDI show the results to be significantly different. The use of NDVI and BDI to study changes in land cover due to urbanization, reduces the time taken to manually classify moderate resolution satellite imagery.展开更多
城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban...城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban extraction,BAUA)的结果在城市近郊工业区有缺失现象,以及市中心内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象的问题,以2019年北京、武汉、郑州、西安4个城市建成区为研究对象,首先借助GEE(google earth engine)平台利用Weka Cobweb聚类算法以及形态学后处理,研究了基于夜间灯光数据NPP/VIIRS与Landsat-8数据计算的建筑指数和地表温度相结合的方法对城市建成区(built-up area extraction,BUAE)提取,然后利用不透水面指数和夜间灯光数据结合的方法提取城市建成区,最后对比2种方法的提取结果.研究表明:(1)在BUAE方法中加入(Landsurface temperature,LST)参数,能有效弥补市郊工业区因夜间灯光数据值损失而造成提取建成区缺失的不足.(2)BUAE方法可以一定程度上减弱提取建成区内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象.(3)2种方法在对市郊和市中心城镇化水平差异小的特大城市北京的建成区提取轮廓基本一致,对市郊和市中心城镇化水平差异大的大城市如武汉、西安、郑州提取建成区的轮廓差异较大.相对BAUA方法,BUAE方法在北京,准确度提高了2.1%,在武汉准确度提高了13.9%,在西安准确度提高了10.6%,在郑州提高了9.7%,但BUAE的虚警率也高于BAUA的虚警率.本研究可以为建成区提取提供参考.展开更多
The change of land use plays a major role in the developmental activity of a developing country. Due to rapid growth of urbanisation and dramatic increasing population, the fertile agricultural land has been converted...The change of land use plays a major role in the developmental activity of a developing country. Due to rapid growth of urbanisation and dramatic increasing population, the fertile agricultural land has been converted to built-up area with respect to the demand for housing requirement and to the need for basic infrastructure facilities. The quantum of open space and surface water bodies has also been encroached. There has been a rapid growth of population in Puducherry city from 3.48 million in 1991 to 5.44 million in 2011. Hence the conservation of natural resources becomes one of the major challenges especially in small and medium town. This study was conducted to assess the effect of change on land use in urban agglomeration area of Puducherry city for the duration period from 1997 to 2017. There has been an increase in population in Puducherry city mainly attributed to higher scale of migration from adjoining rural areas and medium town for better education, job opportunities and quality life. Hence, it has been strongly recommended for stringent Development Control Regulations to quantify the urban sprawl and manage the impact of urbanisation of land use/land cover in Puducherry city.展开更多
By using the latest China population grid and land-use data,we assess the changing exposure of China’s population and land uses to the hazards of storm surges,droughts,earthquakes,floods,and landslides from 1995 to20...By using the latest China population grid and land-use data,we assess the changing exposure of China’s population and land uses to the hazards of storm surges,droughts,earthquakes,floods,and landslides from 1995 to2015.We found that the single-hazard areas and the multihazard areas covered 43%and 26%of China’s territory,respectively.Population grew faster in the hazard-prone areas than in the non-hazard areas.Built-up area expanded more rapidly in the areas prone to earthquakes and landslides.Cropland changed rapidly in many hazard-prone areas.The hazard-prone areas affected by floods featured the highest cropland loss rates,while the areas prone to earthquakes and landslides featured the highest cropland growth rates.We detected areas with significant exposure changes by using hot spot analysis.It was found that population and built-up land in the Pearl River Basin were increasingly exposed to storm surges,floods,and landslides.The Haihe River Basin and Huaihe River Basin also showed a consistent increase of population and built-up land exposure to droughts and earthquakes.These findings can provide a foundation for the design and implementation of protection and adaptation strategies to improve the resilience of Chinese society to natural hazards.展开更多
文摘Designing “liveable” cities as climate change effects are felt all over the world has become a priority to city authorities as ways are sought to reduce rising temperatures in urban areas. Urban Heat Island (UHI) effect occurs when there is a difference in temperature between rural and urban areas. In urban areas, impervious surfaces absorb heat during the day and release it at night, making urban areas warmer compared to rural areas which cool faster at night. This Urban Heat Island effect is particularly noticeable at night. Noticeable negative effects of Urban Heat Islands include health problems, air pollution, water shortages and higher energy requirements. The main objective of this research paper was to analyze the spatial and temporal relationship between Land Surface Temperature (LST) and Normalized Density Vegetation Index (NDVI) and Built-Up Density Index (BDI) in Upper-Hill, Nairobi Kenya. The changes in land cover would be represented by analyzing the two indices NDVI and BDI. Results showed the greatest increase in temperature within Upper-Hill of up to 3.96°C between the years 2015 and 2017. There was also an increase in impervious surfaces as indicated by NDVI and BDI within Upper-Hill and its surroundings. The linear regression results showed a negative correlation between LST and NDVI and a positive correlation with BDI, which is a better predictor of Land Surface Temperature than NDVI. Data sets were analyzed from Landsat imagery for the periods 1987, 2002, 2015 and 2017 to determine changes in land surface temperatures over a 30 year period and it’s relation to land cover changes using indices. Visual comparisons between Temperature differences between the years revealed that temperatures decreased around the urban areas. Minimum and maximum temperatures showed an increase of 1.6°C and 3.65°C respectively between 1987 and 2017. The comparisons between LST, NDVI and BDI show the results to be significantly different. The use of NDVI and BDI to study changes in land cover due to urbanization, reduces the time taken to manually classify moderate resolution satellite imagery.
文摘城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban extraction,BAUA)的结果在城市近郊工业区有缺失现象,以及市中心内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象的问题,以2019年北京、武汉、郑州、西安4个城市建成区为研究对象,首先借助GEE(google earth engine)平台利用Weka Cobweb聚类算法以及形态学后处理,研究了基于夜间灯光数据NPP/VIIRS与Landsat-8数据计算的建筑指数和地表温度相结合的方法对城市建成区(built-up area extraction,BUAE)提取,然后利用不透水面指数和夜间灯光数据结合的方法提取城市建成区,最后对比2种方法的提取结果.研究表明:(1)在BUAE方法中加入(Landsurface temperature,LST)参数,能有效弥补市郊工业区因夜间灯光数据值损失而造成提取建成区缺失的不足.(2)BUAE方法可以一定程度上减弱提取建成区内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象.(3)2种方法在对市郊和市中心城镇化水平差异小的特大城市北京的建成区提取轮廓基本一致,对市郊和市中心城镇化水平差异大的大城市如武汉、西安、郑州提取建成区的轮廓差异较大.相对BAUA方法,BUAE方法在北京,准确度提高了2.1%,在武汉准确度提高了13.9%,在西安准确度提高了10.6%,在郑州提高了9.7%,但BUAE的虚警率也高于BAUA的虚警率.本研究可以为建成区提取提供参考.
文摘The change of land use plays a major role in the developmental activity of a developing country. Due to rapid growth of urbanisation and dramatic increasing population, the fertile agricultural land has been converted to built-up area with respect to the demand for housing requirement and to the need for basic infrastructure facilities. The quantum of open space and surface water bodies has also been encroached. There has been a rapid growth of population in Puducherry city from 3.48 million in 1991 to 5.44 million in 2011. Hence the conservation of natural resources becomes one of the major challenges especially in small and medium town. This study was conducted to assess the effect of change on land use in urban agglomeration area of Puducherry city for the duration period from 1997 to 2017. There has been an increase in population in Puducherry city mainly attributed to higher scale of migration from adjoining rural areas and medium town for better education, job opportunities and quality life. Hence, it has been strongly recommended for stringent Development Control Regulations to quantify the urban sprawl and manage the impact of urbanisation of land use/land cover in Puducherry city.
基金supported by the National Key R&D Program of China(2017YFA0604401)the National Natural Science Foundation of China(Grant Nos.41871306 and 41601420)+1 种基金the Key National Natural Science Foundation of China(Grant No.41531176)the research fund from Shenzhen Key Laboratory of Spatial Smart Sensing and Service.
文摘By using the latest China population grid and land-use data,we assess the changing exposure of China’s population and land uses to the hazards of storm surges,droughts,earthquakes,floods,and landslides from 1995 to2015.We found that the single-hazard areas and the multihazard areas covered 43%and 26%of China’s territory,respectively.Population grew faster in the hazard-prone areas than in the non-hazard areas.Built-up area expanded more rapidly in the areas prone to earthquakes and landslides.Cropland changed rapidly in many hazard-prone areas.The hazard-prone areas affected by floods featured the highest cropland loss rates,while the areas prone to earthquakes and landslides featured the highest cropland growth rates.We detected areas with significant exposure changes by using hot spot analysis.It was found that population and built-up land in the Pearl River Basin were increasingly exposed to storm surges,floods,and landslides.The Haihe River Basin and Huaihe River Basin also showed a consistent increase of population and built-up land exposure to droughts and earthquakes.These findings can provide a foundation for the design and implementation of protection and adaptation strategies to improve the resilience of Chinese society to natural hazards.
