Rapid urban sprawl has been evident in sub-Saharan Africa; however, little is known about the implication on urban energy fluxes. Thus, this study analyses the urban expansion processes of Lagos, Nigeria, a hot-humid and Africa’s most populous city between 2000 – 2020; and quantifies the effect of the associated urban form and function on the partitioning of Surface Energy fluxes in the study period using the Surface Urban Energy and Water Balance Scheme (SUEWS). The urban canopy was parameterized for the years 2000 and 2020 using the Local Climate Zone Scheme via the LCZ generator (https://lcz-generator.rub.de/).
Most of the LCZs are built types, corresponding to LCZ 1 and 2 in the microcenter, LCZ 3 in the macrocenter, and LCZ 6 and 9 in the city suburban area. Results showed a significant increase of 60%, 105% and 165% in LCZ 3, 6 and 9, respectively within the 20 years period at the detriment of 35%, 85%, and 55% loss in the vegetation classes, LCZ A, C, and F respectively. The impact of these landscape changes on the energy fluxes was accessed with SUEWS model forced with ERA5 surface data. Model validation exercise showed an acceptable comparison between modelled and observed meteorological outputs which align with previous findings for midlatitude regions, suggesting that the model could perform well in a humid tropical climate. The spatio-temporal distributions of SEB showed that the turbulent heat fluxes increased significantly particularly in the micro and macro urban LCZs whereas suburban LCZs have greater latent heat flux magnitudes due to the large conversion of vegetation to suburban LCZs. We also noted a significant increase in the Bowen ratio in micro-urban LCZs particularly at night which is marked by great variability across other LCZs. Similarly, we observed a 96% increase in anthropogenic heat flux in all the urban LCZs with marked intra-urban variabilities.
The results demonstrate the capability of SUEWS model with readily available inputs in estimating changes in the surface energy balance because of urbanization in a tropical humid city.
How to cite: Obe, B., Morakinyo, T. E., and Mills, G.: Modelling the Urbanization Effect on Urban Energy Fluxes over a Tropical Humid City, Lagos, Nigeria using SUEWS , EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-147, https://doi.org/10.5194/ems2022-147, 2022.
