The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich...The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.展开更多
Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold islan...Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold island effect(OCIE) intensity, spatial-temporal variation of OCIE, factors influencing the OCIE and impacts of OCIE on air temperature using geographical statistics and GIS methods based on the MODIS land surface temperature, land use/cover change(LUCC) and observed air temperature data. Results showed that all the oases in the Tarim Basin exhibited cold island effects, with the OCIE intensity highest in summer(-9.08°C), followed by autumn(-4.24°C) and spring(-3.85°C). The total area of oasis cold island(OCI) and the comprehensive OCIE index showed the same seasonal change trend as the OCIE intensity. However, the changing trends in areas of OCI with strong, medium and weak OCIEs were inconsistent across different seasons. Farmland and water areas were found to be the key contributors that affected the OCIE, and the area and aggregation metrics of these two land use/cover types directly contributed to the OCIE. By contrast, natural vegetation, such as forest and grassland, almost had no contribution to the OCIE. Simulation of observed air temperature data showed that if farmland is replaced by forest or grassland in the oasis, the mean, maximum and minimum air temperatures will increase significantly. This heating effect will be higher in summer(reaching 1.14°C to 2.08°C) and lower in spring and autumn. Moreover, the heating effect of farmland being replaced by forest will be higher than that of farmland being replaced by grassland. These results can provide a basis for understanding the cold island effect of oases in arid regions.展开更多
为了研究首都功能核心区新建小型城市森林公园缓解城市热岛效应的能力,以广阳谷城市森林公园为研究对象,基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)完成了2014年、2017年和2019年公园内及周边区域...为了研究首都功能核心区新建小型城市森林公园缓解城市热岛效应的能力,以广阳谷城市森林公园为研究对象,基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)完成了2014年、2017年和2019年公园内及周边区域的地表温度反演,同时结合长期定点监测公园内外空气温湿度,分析城市森林公园内及周边冷岛效应。结果发现:广阳谷城市森林公园建成后,在园外100 m范围内有一定的降温效果。相比建成前,2017年和2019年其100 m缓冲区内热岛区域占比分别减少了4.83%和1.38%,地表平均温度比核心区分别降低了0.72℃和1.15℃,说明公园建成以来,充分发挥了冷岛作用;公园内各测点在10:00—17:00的平均温度低于对照点1.65℃,公园内部的相对湿度比对照点高2.68%;3—8月公园内各点的平均温度比对照点低0.67℃,在3月、4月、6月和7月公园内各点的平均湿度比对照点高1.82%,说明森林公园在此段时间发挥着降温增湿的作用。展开更多
基金Under the auspices of National Natural Science Foundation of China(No.41101039,41371068)
文摘The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.
基金funded by the National Natural Science Foundation of China(41571109)
文摘Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold island effect(OCIE) intensity, spatial-temporal variation of OCIE, factors influencing the OCIE and impacts of OCIE on air temperature using geographical statistics and GIS methods based on the MODIS land surface temperature, land use/cover change(LUCC) and observed air temperature data. Results showed that all the oases in the Tarim Basin exhibited cold island effects, with the OCIE intensity highest in summer(-9.08°C), followed by autumn(-4.24°C) and spring(-3.85°C). The total area of oasis cold island(OCI) and the comprehensive OCIE index showed the same seasonal change trend as the OCIE intensity. However, the changing trends in areas of OCI with strong, medium and weak OCIEs were inconsistent across different seasons. Farmland and water areas were found to be the key contributors that affected the OCIE, and the area and aggregation metrics of these two land use/cover types directly contributed to the OCIE. By contrast, natural vegetation, such as forest and grassland, almost had no contribution to the OCIE. Simulation of observed air temperature data showed that if farmland is replaced by forest or grassland in the oasis, the mean, maximum and minimum air temperatures will increase significantly. This heating effect will be higher in summer(reaching 1.14°C to 2.08°C) and lower in spring and autumn. Moreover, the heating effect of farmland being replaced by forest will be higher than that of farmland being replaced by grassland. These results can provide a basis for understanding the cold island effect of oases in arid regions.
