Master Thesis defense by Jonathan Hove Appel

Title: Impacts of Urbanization on Urban Climate in Paris

Abstract:
This study presents a case study of the urban heat island in Paris and its effect on the planetary boundary layer using the combined numerical weather prediction and chemical transport model Enviro-HIRLAM. The land-surface parameters that represent Paris in the model have been changed to those from the Local Climate Zones (LCZ) in the World Urban Database and Access Portal Tool. Human activity is represented by the addition of anthropogenic heat flux (AHF) to the model’s urbantiles. This study aims to evaluate the response of Enviro-HIRLAM to the surface changes combining LCZ classes with AHF, which is carried out through a sensitivity study of the diagnosed 2 meter temperature. An evaluation of the model’s ability to reproduce the observed UHI magnitude in the canopy layer is also performed. Both the sensitivity test and the meteorological evaluation show that land-use change alone is not sufficient to simulate the increased urban temperatures and capture the UHI signal. The addition of anthropogenic heat of 211 W/m2 is required to reproduce the observed UHI magnitude of 3.9◦C and its diurnal cycle. The study also analyzes how the surface change and AHF influences the planetary boundary layer over Paris and the local air pollution. The model shows that increased urbanization leads to a less stratified nocturnal boundary layer and to more vertical mixing of the pollutants.

Supervisor: Jens Hesselbjerg Christensen
Censor: Peter L. Langen (AU)