TITLE:
Analysis of the Relationship between Land Surface Temperature and Vegetation and Built-Up Indices in Upper-Hill, Nairobi
AUTHORS:
Patricia Wanjiku Mwangi, Faith Njoki Karanja, Peter Kariuki Kamau
KEYWORDS:
Urban Heat Island, Built-Up Areas, BDI, Land Surface Temperature
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.6 No.1,
January
12,
2018
ABSTRACT: Designing
“liveable” cities as climate change effects are felt all over the world has become a priority to city authorities as ways are sought to reduce rising
temperatures in urban areas. Urban Heat Island (UHI) effect occurs when there
is a difference in temperature between rural and urban areas. In urban areas,
impervious surfaces absorb heat during the day and release it at night, making
urban areas warmer compared to rural areas which cool faster at night. This
Urban Heat Island effect is particularly noticeable at night. Noticeable
negative effects of Urban Heat Islands include health problems, air pollution,
water shortages and higher energy requirements. The main objective of this
research paper was to analyze the spatial and temporal relationship between
Land Surface Temperature (LST) and
Normalized Density Vegetation Index (NDVI) and Built-Up Density Index (BDI) in Upper-Hill, Nairobi Kenya. The
changes in land cover would be represented by analyzing the two indices NDVI
and BDI. Results showed the greatest
increase in temperature within Upper-Hill of up to 3.96°C between the years
2015 and 2017. There was also an increase in impervious surfaces as indicated
by NDVI and BDI within Upper-Hill and
its surroundings. The linear regression results showed a negative correlation
between LST and NDVI and a positive correlation with BDI, which is a better predictor of Land Surface Temperature than NDVI. Data sets were analyzed from
Landsat imagery for the periods 1987, 2002, 2015 and 2017 to determine changes
in land surface temperatures over a 30 year period and it’s relation to land
cover changes using indices. Visual comparisons between Temperature differences
between the years revealed that temperatures decreased around the urban areas. Minimum and maximum temperatures
showed an increase of 1.6°C and 3.65°C respectively between 1987 and
2017. The comparisons between LST, NDVI and BDI show the results to be significantly different. The use of NDVI and BDI to study changes in land cover due to urbanization, reduces the time
taken to manually classify moderate resolution satellite imagery.