Dynamics of thermal inertia over highly urban city: a case study of Delhi

Abstract

This paper focuses on thermal inertia estimation of Delhi and its surrounding areas during summer season based on the diurnal temperature variations and albedo information of the region retrieved from satellite data. The study involves mapping of day and night time surface temperatures and the blue sky albedo (actual albedo on ground) over the study region using Moderate Resolution Imaging Spectroradiometer (MODIS) datasets. The study reveals that Delhi is cooler than its surrounding regions during the day time, showing the formation of cool island. On the contrary, temperature inside the city is much higher than its surrounding rural regions during the night time, thus confirming the formation of nocturnal heat island. The day and night time temperature maps are then used to obtain the diurnal temperature range and together with albedo maps of the study region, are used to estimate the thermal inertia over the region. The study reveals that the dense built-up urban area of Delhi has higher thermal inertia than that of the surrounding rural areas during the summer season. The spatial variation of thermal inertia over the region is found to explain the occurrence of day-time cool island reasonably well.