Quantifying the spatial and temporal relationship between air and land surface temperatures of different land-cover types in Southeastern China

This study has been carried out to assesses the relationship between land surface temperatures (LST) and changes of land cover (LC) for a part of Najaf Governorate, by using Landsat TM/ETM+ data over the period from1990 to 2009. Landsat TM/ETM+ images have been acquired for deriving the land use/land cover (LULC) maps and land surface temperatures (LST) for two different dates afterwards analysis their temporal and spatial variations. (LST) maps have been derived from thermal infrared (TIR) bands of Landsat TM/ETM+ data according to Planckâ€™s function. Satellite images for 1990, and 2009 have been classified into four classes (building up, vegetation, bare land, and water bodies) based on the supervised classification by using Maximum Likelihood algorithm. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) have been calculated from both the original image in order to extract a particular (LC) for study area. The results of study showed that built-up area increased from 22.1% to 41.8 % between 1990 and 2009, while vegetations, bare land and water bodies decreased from 57.5% to 39.9% , 16.9% to 15.3% , and 3.5% to 3% respectively , due to urbanization that resulted from growing of urban population and economic evolution, . In general the negative correlation between LST and NDVI confirm that the reduction in vegetarian cover to built-up would lead to increase in (LST). Whereas the positive correlation between LST and NDBI implying that the increasing built-up land can increase (LST). The results indicated that the stronger negative correlations between LST and NDVI (R2=0.918) was in 2009 year , and the stronger positive correlation between LST and NDBI (R2=0.909) was in 2009. The results showed that the maximum temperature in study area increased from 32 áµ’C in 1990 to 37áµ’C in 1990 .This research has been confirmed the strong influence of changes in (LC) on (LST).

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Cooling Effect of Different Land Cover Types: A Case Study in Xi’an and Xianyang, China

Sustainability ◽

10.3390/su13031099 ◽

2021 ◽

Vol 13 (3) ◽

pp. 1099

Author(s):

Yuhe Ma ◽

Mudan Zhao ◽

Jianbo Li ◽

Jian Wang ◽

Lifa Hu

Keyword(s):

Land Cover ◽

Surface Temperature ◽

Urban Heat Island ◽

Land Surface Temperature ◽

Land Surface ◽

Cooling Effect ◽

Heat Island ◽

Land Cover Types ◽

Island Effect ◽

Urban Heat

One of the climate problems caused by rapid urbanization is the urban heat island effect, which directly threatens the human survival environment. In general, some land cover types, such as vegetation and water, are generally considered to alleviate the urban heat island effect, because these landscapes can significantly reduce the temperature of the surrounding environment, known as the cold island effect. However, this phenomenon varies over different geographical locations, climates, and other environmental factors. Therefore, how to reasonably configure these land cover types with the cooling effect from the perspective of urban planning is a great challenge, and it is necessary to find the regularity of this effect by designing experiments in more cities. In this study, land cover (LC) classification and land surface temperature (LST) of Xi’an, Xianyang and its surrounding areas were obtained by Landsat-8 images. The land types with cooling effect were identified and their ideal configuration was discussed through grid analysis, distance analysis, landscape index analysis and correlation analysis. The results showed that an obvious cooling effect occurred in both woodland and water at different spatial scales. The cooling distance of woodland is 330 m, much more than that of water (180 m), but the land surface temperature around water decreased more than that around the woodland within the cooling distance. In the specific urban planning cases, woodland can be designed with a complex shape, high tree planting density and large planting areas while water bodies with large patch areas to cool the densely built-up areas. The results of this study have utility for researchers, urban planners and urban designers seeking how to efficiently and reasonably rearrange landscapes with cooling effect and in urban land design, which is of great significance to improve urban heat island problem.

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