A Synthesized Effect of Urban Modification and Net Radiation on the Climate of Lagos Metropolis, Nigeria

Abstract

Land cover adjustment which includes urban landscaping, agriculture crops or hardscapes for
constructing and parking lots promote variations in the energy and radiation balance. Due to
the above listed modifications, the surface temperatures and near-surface air temperatures over
urban patches are generally higher than those over rural areas, thus resulting in an Urban Heat
Island (UHI). In this study, urban landscape and Land Surface Temperature (LST), net
radiation, and Normalized Difference Vegetation Index (NDVI) data were extracted using
remote sensing and GIS (Geographic Information System) were used to synthesize effect of
urban modification and net radiation on the climate of Lagos metropolis. The urban landscape
was estimated and a rapid increase was witness in the urban built-up area, 54.05 km2 between
1984–2000, 270.02 km2 between 2000–2013 With a reductions in rural built-up area, urbanized
open land, rural open land and water body between 1984–2000 and 2000–2013 this reveals
that a wide margin is observed to exist between urban built-up and rural built-up area which
implies that Lagos metropolis is highly urbanized. LST was found to have a mean of 23.05°C
for 1984, 25.99°C for 2000, and 26.66°C for 2013. Net radiation was found to have a mean of
449.43 W/m-2

for 1984, 376.80 W/m-2

for 2000, and 253.48 W/m-2

for 2013. In synthesizing the
effects of factors of urban climate on Lagos metropolis factor analysis used and following
factors were identified such: urbanized area, NDVI, LST, and net radiation. And a significant
correlation exists between listed factors in Lagos metropolis. The result reveals that two factors
were selected: (1) the effect of urbanization on LST and urban surface modification (using
NDVI) and (2) the effect of LST on urban climate due to effect of net radiation. Based on the
selected components, UHI areas were determined for Lagos metropolis using the urbanized
area to delineate the urban built-up area from the rural built-up area, with reference to LST.
Based on research findings, possible mitigation measures as means of controlling the menace
of the UHI were highlighted for the study area.