Investigation of the Impact of Urbanization Under the 2015 Delhi Heat Wave Scenario

In this study, we seek to better understand the role of urbanization in an advectively dominant scenario, such as a heat wave. The 2015 Delhi Heat Wave, recorded as the fifth deadliest in world history as per the International Disaster Database, is taken as a case study. Following a preliminary observational analysis, the temperature, moisture and aerodynamic characteristics are analyzed under multiple urbanization scenarios, for the aforementioned synoptic set up. For this purpose, the surface boundary conditions in a mesoscale model are modified through the integration of land use information from historic Landsat imagery. The results from these numerical experiments are then compared against the ideal ‘All Urban’ or ‘All Rural’ scenarios. The Heat Index is used as an indicator for thermal comfort and analyzed under the multiple scenarios in comparison to observations.

In the next set of experiments, the land surface is then classified in to ten urban categories using the Local Climate Zones classification, along with the incorporation of an anthropogenic flux term.This classification improves upon the treatment of urban areas as mere impervious regions and provides a more realistic representation, by parameterizing the canopy scale dynamics on to the mesoscale. These parameters allow us to observe the cascading effect of thermal gradients and heat fluxes within the city, resulting in an improved representation of the convective activity.

The overall theme is to understand the impact of regional scale forcing in the context of larger scale forcings, towards intensifying an extreme heat wave scenario. Findings from this study will hopefully form a stepping stone towards more informed mitigative measures at a regional scale when subject to such extreme stressors.