| Rapid urbanization process is always accompanied by a large number of problems, the rapid increase of urban population and building density, the summer heat, poor ventilation conditions affect the quality of the living environment. Fuzhou city as the river basin, surrounded by mountains, terrain occlusion, static wind frequency. This paper analyzes the Fuzhou city urban heat island effect, to explore the mitigation of the heat island effect of ventilation pattern planning strategy.Landsat 8 remote sensing images as the data source, in the main urban area of Fuzhou as the research area. Firstly, the surface temperature was retrieved by the thermal infrared band of the image, and the distribution pattern of urban thermal environment in the main city of Fuzhou was obtained. Secondly, the use of remote sensing image to classify the land use of the study area, analysis of the impact of land use on urban heat island effect. Combined with the research area of urban heat island intensity, urban heat environment spatial distribution and the geographical environment, wind speed meteorological parameters analysis. According to the existing urban pattern of urban water system and inland river network to find the potential ventilation pattern, the ventilation pattern planning strategy of the main urban area of Fuzhou was proposed:Thermal infrared band of Landsat 8 Remote Sensing image was used to inverse Land Surface Temperature to obtain thermal environment data of main urban of Fuzhou city, combining field research to analyze phenomenon and causes of the heat island. This study analyzed urban heat island affected by land use type through carrying on land use classification of images of the same period. According to land use type, the distribution of the heat island intense and urban spatial thermal environment, geographic environment, temperature, wind speed and other meteorological parameters were used to search potential ventilation pattern and propose feasibility program with advantages of developed inland water systems and networks in Fuzhou and with existing urban form and the prevailing wind direction.(1) research in 2015 September 27, Landsat 8 remote sensing image as data source, using radiative transfer equation method for the inversion of surface temperature, the results showed that:in the main urban area of Fuzhou average surface temperature for 34.60℃, temperature range for 25.17℃-49.09℃.(2)Standard deviation classification was used to divided Land Surface Temperature which was inversed into 7 grades. According to the formula T=A±χ*sd, T represents the temperature threshold, A represents the average surface temperature in the main city of Fuzhou., sd represents the surface temperature variance in the study area, x represents the variance of the multiple(a value of 0.5,1.5,2.5).They were strong cold island effect area (25.17℃-25.57℃), the cold island effect area (25.58℃～-29.19℃), a weak cold island effect area (29.20℃ ～32.80℃), no significant effect area (32.81℃～36.42℃), low heat island area (36.43℃ ～40.03℃), the heat island area (40.03℃～43.65℃),strong heat island area (43.65℃ ～49.09℃).Further to analyze Spatial distribution characteristics of urban thermal environment, the result showed that UHI core (43℃ above) was mostly impervious surface, and concentrated and formed significant regional, where land use was simple. In space, Heat island contiguous area (40℃ above), that was a large contiguous area, were both the region of more industry gathering. And low regulatory region were mainly covered by water (such as Minjiang River, river, lakes, etc.) and large-scale urban vegetation.(3) According to the classification system of land resources in China, combined with the actual situation of land use in Fuzhou and the classification of remote sensing image. Studies using maximum likelihood supervised classification method of Fuzhou city land use types into grassland, water, roads, construction land, unused land, woodland, farmland, precision analysis is done using the error matrix, results showed that:The overall classification accuracy of remote sensing image map is 93.17%, the Kappa coefficient is 0.89, and the land use classification meets the needs of research.Comparing all over the area occupied by each class was found other construction land>forest>water>farmland>road>unused land>grass, where the area of construction was 111.87km2, accounting for 43.46% of the total area.The area of road was up to 28.76km2, accounting for 11.17% of the total area. Water area of urban, including Minjiang River, Inland waterway, lake, reservoir was up to 32.14km2, accounting for 12.48% of the total area. The area of woodland was up to 36.86km2, accounting for 14.32% of the total area. And unused land was accounted for 7.82%. Regional Structure of land use in Fuzhou City was significant difference, which showed a higher distribution proportion of water area, woodland, road and other construction land, and considerable unused land.(4)The average surface temperature of the seven types sorted from high to low were other construction land>road>unused land>grass>farmland>forest>water. The lowest average surface temperature of water was 28℃ which was maximum gap with the average surface temperature of other land types. Using statistical analysis area of arcgis10.2, the result showed that water is the largest component of the medium cool island effect area, occupied with 88.51%, where Minjiang River and Wulong River Basin is accounting for 83.32%, and cooling effect of large of water area was remarkable. Construction land,including transport and other construction land, were land use type of the highest urban Land Surface Temperature, followed by Land Surface Temperature of unused land, when Grassland, cultivated land was not obvious heat island effect but the temperature changed largely. Guangming Port,other Lakes and reservoirs is accounting for 2%. Moreover, urban forest was 9% of the area of the medium cool island effect, and there were significantly correlation between and cool island grades and mountain elevation.(5)By analyzing the existing urban form and mining existing ventilation corridor, this study research potential ventilation pattern to propose feasibility.According to the principles of overall planning communication with each other, combining with the prevailing wind direction and local circulation and environmental preferentially avoiding pollution, and in accordance with construction mode of vents, cooling node and ventilation road, the Built-up area which was urban of Fuzhou city were carried on ventilation pattern transformation, developed a corresponding program and control index and develop south eastern Minjiang River Valley as the leading southeast wind vent air into the Minjiang River Basin. Rivers and mountains of the study area in strong cool island effect area was selected as A cool node. Furthermore, heat island grade, ecological environment,landscape effects, the ability to adjust microclimate and the location of the surrounding thermal environment were considered synthetically as two cool node.Minjiang River, Wulong River is a major part of the cold island effect area in the study area which was selected as A ventilation Road and selected 40 rivers whose watercourse is wide and whose both sides greenbelt is complete and well maintained as two cool note to construct, and different grades use different control standards.By building Ventilation Road will connect the linear cold island space of urban and cooling node to play a good overall ventilation and cooling effect. To avoid industrial production influences the quality of the surrounding air and even the regional wind environment of 12 through the industrial area of green belt along the river of strict regulation. |
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