Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Influence of urban form on the changing dynamics of surface and canopy layer UHI across the local urban climate zones of Delhi a semi arid megacity

Auteur : Buddhiraja, Bakul

Université de soutenance : Shiv Nadar University

Grade : Doctor of Philosophy (PhD) 2021

Résumé partiel
The urbanization process significantly alters the land use and land cover, causing changes in the climatological interactions between the land surface and the atmosphere. The natural surface energy balance of the earth is disturbed by human intervention, and, although a new equilibrium is attained, it is with a higher diurnal range and adverse effects on the geophysical variables (air temperature, humidity, wind speed and direction, precipitation). The urban fabric stores thermal energy from the incoming shortwave radiation, followed by delayed dissipation in the form of longwave radiation emission, resulting in urban areas being significantly warmer (3-8 ᵒC) than the surrounding rural areas – a phenomenon known as the urban heat island (UHI) effect. The UHI effect of a 3 to 8°C rise in temperature, in addition to the estimated rise in global temperature of about 1.5°C due to climate change, is of grave concern for both human health and the economy. The UHI effect is usually sub-divided into surface UHI, sub-surface UHI, canopy layer UHI and boundary layer UHI. My research aims to understand the influence of urban form on the changing dynamics of the surface and the canopy layer UHI across local climate zones in the city of Delhi. The process most involved in surface UHI is the surface energy balance which determines the land surface temperature. The canopy layer UHI involves both surface energy balance and the energy balance of the air mass above the surface. As a first step, the surface UHI of Delhi has been studied using conventional indicators as well as the relatively new Local climate zone (LCZ) approach. Since the canopy layer processes are interlinked with surface processes, a concurrent study of surface and canopy layer UHI is performed. Three approaches are used- the traverse approach, the fixed-point approach and the automated approach. The warming and cooling rates for various surfaces are observed. The complex relationship between surface and canopy layer UHI are explored in four ‘sub-cities’ of Delhi. The urban form intrinsic to each of the sub-cities creates a distinctive local urban climate. The two contrasting aspects of a sustainable city, i.e., the thermally comfortable local urban climate and socio-economically favourable density are analyzed. A subdued diurnal curve and a high residual temperature is observed for the mix-land use sub city, resettlement colony and industrial city

Présentation et version intégrale (Shodhganga)