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Assessment of Spatio-Temporal and diurnal Urban Heat Island Intensities in Delhi Urban agglomeration using a high resolution Weather Research and Forecasting Model
  • Kshama Gupta,
  • Pushplata Garg,
  • Arijit Roy
Kshama Gupta
Indian Institute of Remote Sensing, Dehradun, India

Corresponding Author:gupta.kshama@gmail.com

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Pushplata Garg
Indian Institute of Technology, Roorkee
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Arijit Roy
Indian Institute of Remote Sensing, Dehradun, India
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Urban Heat Island (UHI) is defi ned as increased surface and air temperatures of urban areas ascompared to rural surroundings. Thermal remote sensing data have been used extensively tostudy Surface Urban Heat Island Intensities (SUHII). However, it fails to provide information ondiurnal profi le of UHI as well as information on Canopy Layer Urban Heat Island Intensities(CLUHII). To overcome these limitations, integrated Weather Research and Forecasting (WRF)-Urban model have been employed in this study to downscale meteorological variables to urbanscale (~500 m) for assessment of spatio-temporal and diurnal profi le of SUHII and CLUHII inDelhi Urban Agglomeration (UA). Delhi UA is third largest UA of the world and largest interstate,densely populated and multi nuclei UA of India. WRF model has been set up with two way nesteddomains of 1.5 km and 0.5 km to take into consideration of local as well as regional weatherphenomenon. Simulations has been carried out for a time period of three days (due tocomputationally intensive simulation) in each season viz. 4-6 June, 2017 in summer season and15-17 January, 2017 in winter season. Evaluation of model performance with ground basedobservations revealed improved RMSE values for Temperature at 2m, wind speed and surfacepressure. Analysis of spatio-temporal and diurnal variability of SUHII in the study region revealedmore UHI during nighttime to morning time (maximum SUHII was observed at 5:30 IST), whereasminimum SUHII value were observed during daytime at 11:30 IST and 14:30 IST in summerseason (Figure 1). As a matter of fact, urban area displayed cool island effect at 11:30 IST.Similar observations were noted while studying the pattern of winter SUHII. Diurnal variability inCLUHII which is computed from model outputs of Temperature at 2m also displayed similarpattern of UHI during winter and summer season as displayed by SUHII. However, in winterCLUHII displayed comparatively more magnitude as compared with winter SUHII. Since, urbanareas displayed lower temperature as compared to its surrounding at 11:30 AM time, the time ofpass of thermal remote sensing satellites (pass time 10:30 AM - 11:30 AM IST) raises concernfor SUHII studies especially in arid and semi-arid regions like Delhi which is surrounded by sand or bare soil that heats up faster than urban built up.