|dc.description.abstract||The impact of land use/ land cover (LULC) changes on urban heat island intensity (UHII), principally caused from urbanization, is investigated with Landsat imagery at Hanoi megacity during the past three decades (1986-2015). For the objective, the primary examinations include (i) the LULC changes caused by urban development in Hanoi during the past three decades (1986 – 2015); (ii) the quantitative analysis of the LULC change impact on Normalized Difference Vegetation Index (NDVI), The Normalized Difference Built-Up Index (NDBI), Land Surface Temperature (LST) and regional precipitation focus on urban growth during past three decades. Hanoi is capital and one of the growing metropolis with the most rapid urbanization speed in Vietnam. It is located in the Northwest of the center of the Red river Delta with coordinates Latitude from 20o 53’ N to 21o 23’ N and Longitude 105o 44’ W and 106o 02’ W.
For this purpose, multi-temporal Landsat images for 1986, 1998, and 2015 were acquired. After I built up LULC classification in 1986, 1998 and 2015, generating a set of random 100 points was done in ArcGIS Map and converting random points to Keyhole Markup Language (KML) in order to open in Google Earth. Each random point’s value verified from Google Earth for accuracy assessment. Google Earth model was used to measure of how many ground truth pixels are correctly classified to validate LULC results. Beside that data ground station about temperature and rainfall also are collected in Hanoi City under period study to validate for LST.
The results of the study showed that LULC in the study area changed significantly with overall classification accuracy of 1986, 1998 and 2015 were 83%, 82% and 84%, with kappa coefficient of 0.79, 0.78 and 0.8, respectively. Finally, UHI effect is determined and the LST values are compared with LULC classes. During 29-year time interval, it was observed that the building area and agricultural land were increased significantly about 282.16 km2 and 440.13 km2, respectively. Maximum LST values were detected for agricultural land, building area, and bare ground, while minimum LST values were detected for water, forest and sandbars classes. The LST is continuously increasing with 4.64 oC in study area over the period under study. Beside that the LST value increases are relatively building and agriculture classes also significantly rose from 1986 to 2015, with the values of 4.94 °C, and 4.74°C, respectively. It was noticed that a positive relationship exists between NDBI and the land surface temperature. On the other side, a negative relationship exists between NDVI and the land surface temperature in Hanoi city. The LST validity of the study results were assessed using real data from four ground stations and the high correlations with R2=0.951, R2=0.935 and R2=0.939 are demonstrated in 1986, 1998 and 2015, respectively. The UHI intensity was computed as 5.71 oC for 1986 and 7.49 oC for 2015. Association the station measurements with UHII, the raising trend in the urban precipitation might be caused by UHI effect, and has positive trend between UHII and fraction rainfall in the urban area. Imperious surface temperature (ISA) value in urban area always higher than rural area and both of them have positive tendency with UHII.||en_US|