Impacts of urbanization on urban heat island (UHI) and meteorological parameters in Hanoi (1998-2016) from ground-based and satellite observations

Hanoi city, the capital of Vietnam, has experienced rapid urbanization since 1990 with the continuous increase of socio-economic indicators. In 2008, implementing the Resolution on administrative boundary adjustment has been helped Hanoi to develop expanding outside the city center. However, the environmental consequences of urban development can cause considerable concern. Therefore, the objective of this study aims at examining the impacts of urbanization in Hanoi focusing on urban heat island (UHI) effect and the changes of meteorological parameters (1998-2016) based on ground-based and satellite observations. The Landsat images at three time-points (1998, 2009 and 2016) were used to produce land use maps identifying the changes in land use patterns over time. To establish the spatial correlation with land surface temperature (LST) map, the normalized difference vegetation index (NDVI) and the normalized difference built-up index (NDBI) maps were employed. The results indicate that the less vegetation content in city center causes higher LST and NDBI values when compared with surrounding areas. The positive correlation between LST and NDBI and the negative correlation between LST and NDVI across all three time-points confirm the influence of urbanization on the formation of UHI. In addition, the intensified UHI has been driven by the increase in urbanization indicators based on the regression analysis. Furthermore, the analysis on meteorological data reveals that urbanization also has impacts on climatic indicators including relative humidity, total rainfall, temperature and wind speed in both urban and rural areas. The overall results might imply that urbanization and its impacts on the environment are challenges to the sustainable development of an increasingly urbanized Hanoi, which should be paid more attention.