scholarly journals Investigation of Urbanization Effects on Land Surface Phenology in Northeast China during 2001–2015

2017 ◽  
Author(s):  
Rui Yao ◽  
Lunche Wang ◽  
Xin Huang ◽  
Xian Guo ◽  
Zigeng Niu ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Rural Area ◽  
Land Surface ◽  
Northeast China ◽  
Growing Season ◽  
Temporal Variations ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Land Surface Phenology ◽  
Urban Heat

The urbanization effects on land surface phenology (LSP) have been investigated by many studies, but few studies focused on the temporal variations of urbanization effects on LSP. In this study, we used the MODIS EVI, MODIS LST data and China’s Land Use/Cover Datasets (CLUDs) to investigate the temporal variations of urban heat island intensity and urbanization effects on LSP in Northeast China during 2001–2015. Land surface temperature (LST) and phenology differences between urban and rural areas represented the urban heat island intensity and urbanization effects on LSP, respectively. Mann-kendall nonparametric test and Sen's slope were used to evaluating the trends of urbanization effects on LSP and urban heat island intensity. The results indicated that the average land surface phenology (LSP) during 2001–2015 was characterized by high spatial heterogeneity. The start of the growing season (SOS) in old urban area had become earlier and earlier than rural area and the differences of SOS between urbanized area and the rural area changed greatly during 2001–2015 (−0.79 days/year, p < 0.01). Meanwhile, the length of the growing season (LOS) in urban and adjacent areas had become increasingly longer than rural area especially in urbanized area (0.92 days/year, p < 0.01), but the differences of the end of the growing season (EOS) between urban and adjacent areas did not change significantly. Next, the UHII increased in spring and autumn during the whole study period. Moreover, the correlation analysis indicated that the increasing urban heat island intensity in spring contributed greatly to the increases of urbanization effects on SOS, but the increasing urban heat island intensity in autumn did not lead to the increases of urbanization effects on EOS in Northeast China.

scholarly journals Effect of Land Cover Fractions on Changes in Surface Urban Heat Islands Using Landsat Time-Series Images

2019 ◽  
Vol 16 (6) ◽  
pp. 971 ◽  
Author(s):  
Tao Chen ◽  
Anchang Sun ◽  
Ruiqing Niu
Keyword(s):  
Land Cover ◽  
Urban Heat Island ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Impervious Surfaces ◽  
Heat Islands ◽  
Urban Heat ◽  
Surface Urban Heat Island

Man-made materials now cover a dominant proportion of urban areas, and such conditions not only change the absorption of solar radiation, but also the allocation of the solar radiation and cause the surface urban heat island effect, which is considered a serious problem associated with the deterioration of urban environments. Although numerous studies have been performed on surface urban heat islands, only a few have focused on the effect of land cover changes on surface urban heat islands over a long time period. Using six Landsat image scenes of the Metropolitan Development Area of Wuhan, our experiment (1) applied a mapping method for normalized land surface temperatures with three land cover fractions, which were impervious surfaces, non-chlorophyllous vegetation and soil and vegetation fractions, and (2) performed a fitting analysis of fierce change areas in the surface urban heat island intensity based on a time trajectory. Thematic thermal maps were drawn to analyze the distribution of and variations in the surface urban heat island in the study area. A Multiple Endmember Spectral Mixture Analysis was used to extract the land cover fraction information. Then, six ternary triangle contour graphics were drawn based on the land surface temperature and land cover fraction information. A time trajectory was created to summarize the changing characteristics of the surface urban heat island intensity. A fitting analysis was conducted for areas showing fierce changes in the urban heat intensity. Our results revealed that impervious surfaces had the largest impacts on surface urban heat island intensity, followed by the non-chlorophyllous vegetation and soil fraction. Moreover, the results indicated that the vegetation fraction can alleviate the occurrence of surface urban heat islands. These results reveal the impact of the land cover fractions on surface urban heat islands. Urban expansion generates impervious artificial objects that replace pervious natural objects, which causes an increase in land surface temperature and results in a surface urban heat island.

scholarly journals Appraisal of Urban Heat Island over Gujranwala and its Environmental Impact Assessment using Satellite Imagery (1995-2016).

2019 ◽  
Vol 01 (01) ◽  
Author(s):  
Syeda Areeba Gillani ◽  
Saif-ul- Rehman ◽  
Hafiz Haroon Ahmad ◽  
Abdul Rehman ◽  
Sarwar Ali ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Growth ◽  
Land Surface ◽  
Temporal Variations ◽  
Growth Patterns ◽  
Heat Island ◽  
High Concentration ◽  
Rapid Urbanization ◽  
North West ◽  
Urban Heat

Rapid urbanization and concretization are the main sources of formation and existence of Urban Heat Island (UHI). Due to high concentration of pollutants in urban environments, the residents are exposed to unexpected health issues. This study aims at delineating the temporal variations in the spatial extent of UHI over Gujranwala using Landsat thermal imagery. It also aims at determining the variations in pollutant concentration in the atmosphere due to vehicle’s tailpipe emissions and fossil fuel burning by industrial plants. We used various indices e.g., NDVI, NDBI, NDWI and land surface temperature calculations to investigate spatio-temporal variations in urban growth patterns and their impacts on the UHI. The results show that the UHI enlarged in all direction specially in the north west during the study period which is similar to urban growth trends. There also exist positive correlation between industrial and vehicle’s discharge with pollutant’s concentration in atmosphere. Remote sensing tools proved elegant in trend mapping and analysis.

scholarly journals MONITORING URBAN HEAT ISLAND THROUGH GOOGLE EARTH ENGINE: POTENTIALITIES AND DIFFICULTIES IN DIFFERENT CITIES OF THE UNITED STATES

2018 ◽  
Vol XLII-3 ◽  
pp. 1467-1472 ◽  
Author(s):  
R. Ravanelli ◽  
A. Nascetti ◽  
R. V. Cirigliano ◽  
C. Di Rico ◽  
P. Monti ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Land Surface ◽  
Large Scale ◽  
The United States ◽  
Temporal Variations ◽  
Google Earth ◽  
Heat Island ◽  
Large Scale Analysis ◽  
Urban Heat ◽  
Google Earth Engine

The aim of this work is to exploit the large-scale analysis capabilities of the innovative Google Earth Engine platform in order to investigate the temporal variations of the Urban Heat Island phenomenon as a whole. A intuitive methodology implementing a largescale correlation analysis between the Land Surface Temperature and Land Cover alterations was thus developed.<br>The results obtained for the Phoenix MA are promising and show how the urbanization heavily affects the magnitude of the UHI effects with significant increases in LST. The proposed methodology is therefore able to efficiently monitor the UHI phenomenon.

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