Investigating the Effect of Lockdown During COVID-19 on Land Surface Temperature: Study of Dehradun City, India
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RESEARCH ARTICLE
Investigating the Effect of Lockdown During COVID-19 on Land Surface Temperature: Study of Dehradun City, India Sandeep Maithani1
•
Garima Nautiyal2 • Archana Sharma2
Received: 30 June 2020 / Accepted: 24 August 2020 Ó Indian Society of Remote Sensing 2020
Abstract Urban environment imposes challenges due to its dynamics and thermodynamic characteristics of the built environment. The present study aims to study the effect of lockdown during COVID-19 on the spatio-temporal land surface temperature (LST) patterns in Dehradun city. The TIRS sensor data of 14 April 2020 (post-lockdown), 28 April 2019, 25 April 2018 and 08 May 2017 were downloaded, and LST was retrieved using radiative transfer equation. The wardwise change in LST, urban hot spots and thermal comfort was studied as a function of built-up density. It was observed that there was an overall decrease in LST values in Dehradun city in post-COVID lockdown period. Wards with high built-up density had minimum decrease in LST; on the contrary, wards with large proportion of open spaces and having low, medium built-up density had the maximum decrease in LST. Hot spot analysis was carried out using Getis Ord GI* statistic, and the level of thermal comfort was found using the urban thermal field variance index. It was observed that there was an increase in number of hot spots accompanied by a decrease in thermal comfort level post-lockdown. The methodology proposed in the present study can be applied to other Indian cities which exhibit similar growth patterns and will provide a tool for rational decision making. Keywords Land surface temperature Thermal infrared sensor Radiative transfer equation Hot spot Land surface emissivity Urban thermal field variance index
Introduction The urban growth process can be classified broadly into two modes: urban densification and urban sprawl. Urban densification refers to the increase in the building density in existing built-up areas, while urban sprawl refers to the outward growth of built-up areas on to the contiguous agricultural lands. (Wang and Upreti 2019; Rahman et al. 2011). Both the growth modes result in the conversion of & Sandeep Maithani [email protected] Garima Nautiyal [email protected] Archana Sharma [email protected] 1
Urban and Regional Studies Department, Indian Institute of Remote Sensing, Dehradun, India
2
School of Environment and Natural Resources, Doon University, Dehradun, India
natural land cover (vegetation and pervious areas) into impervious built-up surfaces. The impervious built-up surfaces consist of building material like bitumen, asphalt, brick, concrete, etc. which absorb and store solar radiations during the day and release it gradually at night. Due to the intrinsic nature of building materials (i.e. radiative, thermal, moisture and emission characteristics), external parameters of the built-up areas (i.e. built-up density, urban geometry, orientation of buildings) and near-surface anthropogenic source of heat, the land surface temperatu
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