Assessing The Impacts Of Urban Green Areas On Mitigating Urban Heat Island Effect The Case Of Addis Ababa Ethiopia

Several studies have been conducted on analyzing the land surface temperature sincern1970’s other than Ethiopia in detail. Urban Heat Island (UHI) is the variation in LandrnSurface Temperature (LST) between the urban realm and the surrounding rural areas.rnUrban areas are experiencing large population density, an increase surface temperaturernand expansion of builtuprnenvironment, which this intern affects the microclimaternof therncity and develops UHI. With regard to surface temperature, different parameters andrndata’s were used to understand the situation, to examine its effect and for determining arnsolution to overcome the consequences. Input data’s such as Landsat TM (ThematicrnMapper), ETM+ (Enhanced Thematic Mapper Plus) and Landsat 8 OLI – TIRSrn(Operational Land Imagery – Thermal Infrared Sensor) images, after conductingrnradiometric and geometric corrections, were used to produce results for analysis. Forrngenerating LST of the study area, using Landsat Satellite data, Single and Split WindowrnAlgorithms were applied. Measurement techniques, NDVI (Normalized DifferencernVegetation Index), LST (Land Surface Temperature), NDBI (Normalized DifferencernBuiltuprnIndex) and Landuse/rnLandcoverrnwere produced to examine the UHI effect andrnthe positive influence of green areas. The result in correlating the LST and NDVIrnindicates that, more than 76% of the variability of the LST is due to the distribution ofrnNDVI throughout the study area. Therefore, NDVI as indicator to LST is acceptable,rnbecause, it results in strong correlation. The maximum LST in the four base years (1985,rn1995, 2006 and 2015), with slight decrease in 1995, it shows a gradual increment in thernmeasured LST and area coverage. In 1985, the area under 17⁰�� surface temperaturerncovers 0.95km2, 17–21⁰���������������������������� km2 and 61.6% of the area received temperaturernbetween 27–31⁰���� The result also shows, the higher the value of the NDBI is the higherrnthe LST. A dramatic landuse/rnlandcoverrnchange exhibited from 1985 to 2015. In 1985rnthe builtuprncovers 25.7%, in 1995 about 40.8, in 2006 was 48.31 and in 2015 becomern59.64%. On the other hand, vegetation cover is decreasing from 16.6% to 9.54% for thernyear 1985 and 2015, respectively. Measured temperature in the selected public parks andrnsurroundings, indicates that, there is a maximum of 5⁰�� temperature increment. UrbanrnPublic Parks plays a major role in mitigating the Urban Heat Island Effect. Therefore, arnproper planning should be considered by government and stakeholders for administeringrnand developing green areas and individuals keep the surrounding green.rnKey words: NDVI, NDBI, LST, UHI, Land-use/Land-cover.

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